parser: Remove the unused attribute alignment from struct declaration_specifiers_t.
[cparser] / format_check.c
index e33b0be..d4beefa 100644 (file)
@@ -1,31 +1,19 @@
 /*
  * This file is part of cparser.
- * Copyright (C) 2007-2009 Matthias Braun <matze@braunis.de>
- *
- * This program is free software; you can redistribute it and/or
- * modify it under the terms of the GNU General Public License
- * as published by the Free Software Foundation; either version 2
- * of the License, or (at your option) any later version.
- *
- * This program is distributed in the hope that it will be useful,
- * but WITHOUT ANY WARRANTY; without even the implied warranty of
- * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
- * GNU General Public License for more details.
- *
- * You should have received a copy of the GNU General Public License
- * along with this program; if not, write to the Free Software
- * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA
- * 02111-1307, USA.
+ * Copyright (C) 2012 Matthias Braun <matze@braunis.de>
  */
+#include <config.h>
+
 #include <ctype.h>
-#include <wctype.h>
 
+#include "adt/strutil.h"
 #include "adt/util.h"
 #include "format_check.h"
 #include "symbol_t.h"
 #include "ast_t.h"
 #include "entity_t.h"
 #include "diagnostic.h"
+#include "parser.h"
 #include "types.h"
 #include "type_t.h"
 #include "warning.h"
@@ -87,146 +75,83 @@ static const char* get_length_modifier_name(const format_length_modifier_t mod)
                [FMT_MOD_I32]  = "I32",
                [FMT_MOD_I64]  = "I64"
        };
-       assert(mod < lengthof(names));
+       assert((size_t)mod < lengthof(names));
        return names[mod];
 }
 
-static void warn_invalid_length_modifier(const source_position_t *pos,
+static void warn_invalid_length_modifier(const position_t *pos,
                                          const format_length_modifier_t mod,
-                                         const wchar_rep_t conversion)
-{
-       warningf(pos,
-               "invalid length modifier '%s' for conversion specifier '%%%c'",
-               get_length_modifier_name(mod), conversion
-       );
-}
-
-typedef struct vchar_t vchar_t;
-struct vchar_t {
-       const void *string;   /**< the string */
-       size_t     position;  /**< current position */
-       size_t     size;      /**< size of the string */
-
-       /** return the first character of the string and setthe position to 0. */
-       unsigned (*first)(vchar_t *self);
-       /** return the next character of the string */
-       unsigned (*next)(vchar_t *self);
-       /** return non_zero if the given character is a digit */
-       int (*is_digit)(unsigned vchar);
-};
-
-static unsigned string_first(vchar_t *self)
-{
-       self->position = 0;
-       const string_t *string = self->string;
-       return string->begin[0];
-}
-
-static unsigned string_next(vchar_t *self)
-{
-       ++self->position;
-       const string_t *string = self->string;
-       return string->begin[self->position];
-}
-
-static int string_isdigit(unsigned vchar)
-{
-       return isdigit(vchar);
-}
-
-static unsigned wstring_first(vchar_t *self)
+                                         const char conversion)
 {
-       self->position = 0;
-       const wide_string_t *wstring = self->string;
-       return wstring->begin[0];
-}
-
-static unsigned wstring_next(vchar_t *self)
-{
-       ++self->position;
-       const wide_string_t *wstring = self->string;
-       return wstring->begin[self->position];
-}
-
-static int wstring_isdigit(unsigned vchar)
-{
-       return iswdigit(vchar);
-}
-
-static bool atend(vchar_t *self)
-{
-       return self->position + 1 == self->size;
+       char const *const lmod = get_length_modifier_name(mod);
+       warningf(WARN_FORMAT, pos, "invalid length modifier '%s' for conversion specifier '%%%c'", lmod, conversion);
 }
 
 /**
- * Check printf-style format.
+ * Check printf-style format. Returns number of expected arguments.
  */
-static void check_printf_format(const call_argument_t *arg, const format_spec_t *spec)
+static int internal_check_printf_format(const expression_t *fmt_expr,
+                                        const call_argument_t *arg,
+                                        const format_spec_t *spec)
 {
-       /* find format arg */
-       unsigned idx = 0;
-       for (; idx < spec->fmt_idx; ++idx) {
-               if (arg == NULL)
-                       return;
-               arg = arg->next;
-       }
-
-       const expression_t *fmt_expr = arg->expression;
-       if (fmt_expr->kind == EXPR_UNARY_CAST_IMPLICIT) {
+       while (fmt_expr->kind == EXPR_UNARY_CAST) {
                fmt_expr = fmt_expr->unary.value;
        }
 
-       vchar_t vchar;
-       if (fmt_expr->kind == EXPR_WIDE_STRING_LITERAL) {
-               vchar.string   = &fmt_expr->wide_string.value;
-               vchar.size     = fmt_expr->wide_string.value.size;
-               vchar.first    = wstring_first;
-               vchar.next     = wstring_next;
-               vchar.is_digit = wstring_isdigit;
-       } else if (fmt_expr->kind == EXPR_STRING_LITERAL) {
-               vchar.string   = &fmt_expr->string.value;
-               vchar.size     = fmt_expr->string.value.size;
-               vchar.first    = string_first;
-               vchar.next     = string_next;
-               vchar.is_digit = string_isdigit;
-       } else {
-               return;
+       /*
+        * gettext results in expressions like (X ? "format_string" : Y)
+        * we assume the left part is the format string
+        */
+       if (fmt_expr->kind == EXPR_CONDITIONAL) {
+               conditional_expression_t const *const c = &fmt_expr->conditional;
+               expression_t             const *      t = c->true_expression;
+               if (t == NULL)
+                       t = c->condition;
+               int const nt = internal_check_printf_format(t,                   arg, spec);
+               int const nf = internal_check_printf_format(c->false_expression, arg, spec);
+               return nt > nf ? nt : nf;
        }
-       /* find the real args */
-       for(; idx < spec->arg_idx && arg != NULL; ++idx)
-               arg = arg->next;
 
-       const source_position_t *pos = &fmt_expr->base.source_position;
-       unsigned fmt     = vchar.first(&vchar);
-       unsigned num_fmt = 0;
-       for (; fmt != '\0'; fmt = vchar.next(&vchar)) {
+       if (fmt_expr->kind != EXPR_STRING_LITERAL)
+               return -1;
+
+       const char *string = fmt_expr->string_literal.value.begin;
+       size_t      size   = fmt_expr->string_literal.value.size;
+       const char *c      = string;
+
+       const position_t *pos = &fmt_expr->base.pos;
+       unsigned num_fmt  = 0;
+       unsigned num_args = 0;
+       char     fmt;
+       for (fmt = *c; fmt != '\0'; fmt = *(++c)) {
                if (fmt != '%')
                        continue;
-               fmt = vchar.next(&vchar);
+               fmt = *(++c);
 
                if (fmt == '%')
                        continue;
 
                ++num_fmt;
+               ++num_args;
 
                format_flags_t fmt_flags = FMT_FLAG_NONE;
                if (fmt == '0') {
-                       fmt = vchar.next(&vchar);
+                       fmt = *(++c);
                        fmt_flags |= FMT_FLAG_ZERO;
                }
 
                /* argument selector or minimum field width */
-               if (vchar.is_digit(fmt)) {
+               if (isdigit(fmt)) {
                        do {
-                               fmt = vchar.next(&vchar);
-                       } while (vchar.is_digit(fmt));
+                               fmt = *(++c);
+                       } while (isdigit(fmt));
 
                        /* digit string was ... */
                        if (fmt == '$') {
                                /* ... argument selector */
                                fmt_flags = FMT_FLAG_NONE; /* reset possibly set 0-flag */
                                /* TODO implement */
-                               return;
+                               return -1;
                        }
                        /* ... minimum field width */
                } else {
@@ -241,14 +166,14 @@ static void check_printf_format(const call_argument_t *arg, const format_spec_t
 
                                        case ' ':
                                                if (fmt_flags & FMT_FLAG_PLUS) {
-                                                       warningf(pos, "' ' is overridden by prior '+' in conversion specification %u", num_fmt);
+                                                       warningf(WARN_FORMAT, pos, "' ' is overridden by prior '+' in conversion specification %u", num_fmt);
                                                }
                                                flag = FMT_FLAG_SPACE;
                                                break;
 
                                        case '+':
                                                if (fmt_flags & FMT_FLAG_SPACE) {
-                                                       warningf(pos, "'+' overrides prior ' ' in conversion specification %u", num_fmt);
+                                                       warningf(WARN_FORMAT, pos, "'+' overrides prior ' ' in conversion specification %u", num_fmt);
                                                }
                                                flag = FMT_FLAG_PLUS;
                                                break;
@@ -256,50 +181,56 @@ static void check_printf_format(const call_argument_t *arg, const format_spec_t
                                        default: goto break_fmt_flags;
                                }
                                if (fmt_flags & flag) {
-                                       warningf(pos, "repeated flag '%c' in conversion specification %u", (char)fmt, num_fmt);
+                                       warningf(WARN_FORMAT, pos, "repeated flag '%c' in conversion specification %u", (char)fmt, num_fmt);
                                }
                                fmt_flags |= flag;
-                               fmt = vchar.next(&vchar);
+                               fmt = *(++c);
                        }
 break_fmt_flags:
 
                        /* minimum field width */
                        if (fmt == '*') {
-                               fmt = vchar.next(&vchar);
+                               ++num_args;
+                               fmt = *(++c);
                                if (arg == NULL) {
-                                       warningf(pos, "missing argument for '*' field width in conversion specification %u", num_fmt);
-                                       return;
+                                       warningf(WARN_FORMAT, pos, "missing argument for '*' field width in conversion specification %u", num_fmt);
+                                       return -1;
                                }
                                const type_t *const arg_type = arg->expression->base.type;
                                if (arg_type != type_int) {
-                                       warningf(pos, "argument for '*' field width in conversion specification %u is not an 'int', but an '%T'", num_fmt, arg_type);
+                                       warningf(WARN_FORMAT, pos, "argument for '*' field width in conversion specification %u is not an 'int', but an '%T'", num_fmt, arg_type);
                                }
                                arg = arg->next;
                        } else {
-                               while (vchar.is_digit(fmt)) {
-                                       fmt = vchar.next(&vchar);
+                               while (isdigit(fmt)) {
+                                       fmt = *(++c);
                                }
                        }
                }
 
                /* precision */
                if (fmt == '.') {
-                       fmt = vchar.next(&vchar);
+                       if (fmt_flags & FMT_FLAG_ZERO) {
+                               warningf(WARN_FORMAT, pos, "'0' flag ignored with precision in conversion specification %u", num_fmt);
+                       }
+
+                       ++num_args;
+                       fmt = *(++c);
                        if (fmt == '*') {
-                               fmt = vchar.next(&vchar);
+                               fmt = *(++c);
                                if (arg == NULL) {
-                                       warningf(pos, "missing argument for '*' precision in conversion specification %u", num_fmt);
-                                       return;
+                                       warningf(WARN_FORMAT, pos, "missing argument for '*' precision in conversion specification %u", num_fmt);
+                                       return -1;
                                }
                                const type_t *const arg_type = arg->expression->base.type;
                                if (arg_type != type_int) {
-                                       warningf(pos, "argument for '*' precision in conversion specification %u is not an 'int', but an '%T'", num_fmt, arg_type);
+                                       warningf(WARN_FORMAT, pos, "argument for '*' precision in conversion specification %u is not an 'int', but an '%T'", num_fmt, arg_type);
                                }
                                arg = arg->next;
                        } else {
                                /* digit string may be omitted */
-                               while (vchar.is_digit(fmt)) {
-                                       fmt = vchar.next(&vchar);
+                               while (isdigit(fmt)) {
+                                       fmt = *(++c);
                                }
                        }
                }
@@ -308,9 +239,9 @@ break_fmt_flags:
                format_length_modifier_t fmt_mod;
                switch (fmt) {
                        case 'h':
-                               fmt = vchar.next(&vchar);
+                               fmt = *(++c);
                                if (fmt == 'h') {
-                                       fmt = vchar.next(&vchar);
+                                       fmt = *(++c);
                                        fmt_mod = FMT_MOD_hh;
                                } else {
                                        fmt_mod = FMT_MOD_h;
@@ -318,48 +249,48 @@ break_fmt_flags:
                                break;
 
                        case 'l':
-                               fmt = vchar.next(&vchar);
+                               fmt = *(++c);
                                if (fmt == 'l') {
-                                       fmt = vchar.next(&vchar);
+                                       fmt = *(++c);
                                        fmt_mod = FMT_MOD_ll;
                                } else {
                                        fmt_mod = FMT_MOD_l;
                                }
                                break;
 
-                       case 'L': fmt = vchar.next(&vchar); fmt_mod = FMT_MOD_L;    break;
-                       case 'j': fmt = vchar.next(&vchar); fmt_mod = FMT_MOD_j;    break;
-                       case 't': fmt = vchar.next(&vchar); fmt_mod = FMT_MOD_t;    break;
-                       case 'z': fmt = vchar.next(&vchar); fmt_mod = FMT_MOD_z;    break;
-                       case 'q': fmt = vchar.next(&vchar); fmt_mod = FMT_MOD_q;    break;
+                       case 'L': fmt = *(++c); fmt_mod = FMT_MOD_L;    break;
+                       case 'j': fmt = *(++c); fmt_mod = FMT_MOD_j;    break;
+                       case 't': fmt = *(++c); fmt_mod = FMT_MOD_t;    break;
+                       case 'z': fmt = *(++c); fmt_mod = FMT_MOD_z;    break;
+                       case 'q': fmt = *(++c); fmt_mod = FMT_MOD_q;    break;
                        /* microsoft mode */
                        case 'w':
                                if (c_mode & _MS) {
-                                       fmt = vchar.next(&vchar); fmt_mod = FMT_MOD_w;
+                                       fmt = *(++c); fmt_mod = FMT_MOD_w;
                                } else {
                                        fmt_mod = FMT_MOD_NONE;
                                }
                                break;
                        case 'I':
                                if (c_mode & _MS) {
-                                       fmt = vchar.next(&vchar); fmt_mod = FMT_MOD_I;
+                                       fmt = *(++c); fmt_mod = FMT_MOD_I;
                                        if (fmt == '3') {
-                                               fmt = vchar.next(&vchar);
+                                               fmt = *(++c);
                                                if (fmt == '2') {
-                                                       fmt = vchar.next(&vchar);
+                                                       fmt = *(++c);
                                                        fmt_mod = FMT_MOD_I32;
                                                } else {
                                                        /* rewind */
-                                                       --vchar.position;
+                                                       fmt = *(--c);
                                                }
                                        } else if (fmt == '6') {
-                                               fmt = vchar.next(&vchar);
+                                               fmt = *(++c);
                                                if (fmt == '4') {
-                                                       fmt = vchar.next(&vchar);
+                                                       fmt = *(++c);
                                                        fmt_mod = FMT_MOD_I64;
                                                } else {
                                                        /* rewind */
-                                                       --vchar.position;
+                                                       fmt = *(--c);
                                                }
                                        }
                                } else {
@@ -372,7 +303,7 @@ break_fmt_flags:
                }
 
                if (fmt == '\0') {
-                       warningf(pos, "dangling %% in format string");
+                       warningf(WARN_FORMAT, pos, "dangling %% in format string");
                        break;
                }
 
@@ -383,17 +314,17 @@ break_fmt_flags:
                        case 'd':
                        case 'i':
                                switch (fmt_mod) {
-                                       case FMT_MOD_NONE: expected_type = type_int;       break;
-                                       case FMT_MOD_hh:   expected_type = type_int;       break; /* TODO promoted signed char */
-                                       case FMT_MOD_h:    expected_type = type_int;       break; /* TODO promoted short */
-                                       case FMT_MOD_l:    expected_type = type_long;      break;
-                                       case FMT_MOD_ll:   expected_type = type_long_long; break;
-                                       case FMT_MOD_j:    expected_type = type_intmax_t;  break;
-                                       case FMT_MOD_z:    expected_type = type_ssize_t;   break;
-                                       case FMT_MOD_t:    expected_type = type_ptrdiff_t; break;
-                                       case FMT_MOD_I:    expected_type = type_ptrdiff_t; break;
-                                       case FMT_MOD_I32:  expected_type = type_int32;     break;
-                                       case FMT_MOD_I64:  expected_type = type_int64;     break;
+                                       case FMT_MOD_NONE: expected_type = type_int;         break;
+                                       case FMT_MOD_hh:   expected_type = type_signed_char; break;
+                                       case FMT_MOD_h:    expected_type = type_short;       break;
+                                       case FMT_MOD_l:    expected_type = type_long;        break;
+                                       case FMT_MOD_ll:   expected_type = type_long_long;   break;
+                                       case FMT_MOD_j:    expected_type = type_intmax_t;    break;
+                                       case FMT_MOD_z:    expected_type = type_ssize_t;     break;
+                                       case FMT_MOD_t:    expected_type = type_ptrdiff_t;   break;
+                                       case FMT_MOD_I:    expected_type = type_ptrdiff_t;   break;
+                                       case FMT_MOD_I32:  expected_type = type_int32;       break;
+                                       case FMT_MOD_I64:  expected_type = type_int64;       break;
 
                                        default:
                                                warn_invalid_length_modifier(pos, fmt_mod, fmt);
@@ -413,8 +344,8 @@ break_fmt_flags:
 eval_fmt_mod_unsigned:
                                switch (fmt_mod) {
                                        case FMT_MOD_NONE: expected_type = type_unsigned_int;       break;
-                                       case FMT_MOD_hh:   expected_type = type_int;                break; /* TODO promoted unsigned char */
-                                       case FMT_MOD_h:    expected_type = type_int;                break; /* TODO promoted unsigned short */
+                                       case FMT_MOD_hh:   expected_type = type_unsigned_char;      break;
+                                       case FMT_MOD_h:    expected_type = type_unsigned_short;     break;
                                        case FMT_MOD_l:    expected_type = type_unsigned_long;      break;
                                        case FMT_MOD_ll:   expected_type = type_unsigned_long_long; break;
                                        case FMT_MOD_j:    expected_type = type_uintmax_t;          break;
@@ -525,10 +456,9 @@ eval_fmt_mod_unsigned:
                                break;
 
                        default:
-                               warningf(pos, "encountered unknown conversion specifier '%%%C' at position %u", (wint_t)fmt, num_fmt);
+                               warningf(WARN_FORMAT, pos, "encountered unknown conversion specifier '%%%c' at position %u", fmt, num_fmt);
                                if (arg == NULL) {
-                                       warningf(pos, "too few arguments for format string");
-                                       return;
+                                       goto too_few_args;
                                }
                                goto next_arg;
                }
@@ -545,15 +475,16 @@ eval_fmt_mod_unsigned:
                        if (wrong_flags & FMT_FLAG_TICK)  *p++ = '\'';
                        *p = '\0';
 
-                       warningf(pos, "invalid format flags \"%s\" in conversion specification %%%c at position %u", wrong, fmt, num_fmt);
+                       warningf(WARN_FORMAT, pos, "invalid format flags \"%s\" in conversion specification %%%c at position %u", wrong, fmt, num_fmt);
                }
 
                if (arg == NULL) {
-                       warningf(pos, "too few arguments for format string");
-                       return;
+too_few_args:
+                       warningf(WARN_FORMAT, pos, "too few arguments for format string");
+                       return -1;
                }
 
-               {       /* create a scope here to prevent warning about the jump to next_arg */
+               { /* create a scope here to prevent warning about the jump to next_arg */
                        type_t *const arg_type           = arg->expression->base.type;
                        type_t *const arg_skip           = skip_typeref(arg_type);
                        type_t *const expected_type_skip = skip_typeref(expected_type);
@@ -573,39 +504,72 @@ eval_fmt_mod_unsigned:
                                                goto next_arg;
                                        }
                                }
-                       } else {
-                               if (get_unqualified_type(arg_skip) == expected_type_skip) {
+                       } else if (get_unqualified_type(arg_skip) == expected_type_skip) {
+                               goto next_arg;
+                       } else if (arg->expression->kind == EXPR_UNARY_CAST) {
+                               expression_t const *const expr        = arg->expression->unary.value;
+                               type_t             *const unprom_type = skip_typeref(expr->base.type);
+                               if (get_unqualified_type(unprom_type) == expected_type_skip) {
+                                       goto next_arg;
+                               }
+                               if (expected_type_skip == type_unsigned_int && !is_type_signed(unprom_type)) {
                                        goto next_arg;
                                }
                        }
                        if (is_type_valid(arg_skip)) {
-                               warningf(pos,
-                                       "argument type '%T' does not match conversion specifier '%%%s%c' at position %u",
-                                       arg_type, get_length_modifier_name(fmt_mod), (char)fmt, num_fmt);
+                               position_t const *const apos = &arg->expression->base.pos;
+                               char       const *const mod  = get_length_modifier_name(fmt_mod);
+                               warningf(WARN_FORMAT, apos, "conversion '%%%s%c' at position %u specifies type '%T' but the argument has type '%T'", mod, (char)fmt, num_fmt, expected_type, arg_type);
                        }
                }
 next_arg:
                arg = arg->next;
        }
-       if (!atend(&vchar)) {
-               warningf(pos, "format string contains '\\0'");
+       assert(fmt == '\0');
+       if (c+1 < string + size) {
+               warningf(WARN_FORMAT, pos, "format string contains '\\0'");
        }
-       if (arg != NULL) {
-               unsigned num_args = num_fmt;
-               while (arg != NULL) {
-                       ++num_args;
-                       arg = arg->next;
-               }
-               warningf(pos, "%u argument%s but only %u format specifier%s",
-                       num_args, num_args != 1 ? "s" : "",
-                       num_fmt, num_fmt != 1 ? "s" : "");
+       return num_args;
+}
+
+/**
+ * Check printf-style format.
+ */
+static void check_printf_format(call_argument_t const *arg,
+                                format_spec_t const *const spec)
+{
+       /* find format arg */
+       size_t idx = 0;
+       for (; idx < spec->fmt_idx; ++idx) {
+               if (arg == NULL)
+                       return;
+               arg = arg->next;
+       }
+
+       expression_t const *const fmt_expr = arg->expression;
+
+       /* find the real args */
+       for (; idx < spec->arg_idx && arg != NULL; ++idx)
+               arg = arg->next;
+
+       int const num_fmt = internal_check_printf_format(fmt_expr, arg, spec);
+       if (num_fmt < 0)
+               return;
+
+       size_t num_args = 0;
+       for (; arg != NULL; arg = arg->next)
+               ++num_args;
+       if (num_args > (size_t)num_fmt) {
+               position_t const *const pos = &fmt_expr->base.pos;
+               warningf(WARN_FORMAT, pos, "%u argument%s but only %u format specifier%s", num_args, num_args != 1 ? "s" : "", num_fmt,  num_fmt  != 1 ? "s" : "");
        }
 }
 
 /**
  * Check scanf-style format.
  */
-static void check_scanf_format(const call_argument_t *arg, const format_spec_t *spec)
+static void check_scanf_format(const call_argument_t *arg,
+                               const format_spec_t *spec)
 {
        /* find format arg */
        unsigned idx = 0;
@@ -616,264 +580,296 @@ static void check_scanf_format(const call_argument_t *arg, const format_spec_t *
        }
 
        const expression_t *fmt_expr = arg->expression;
-       if (fmt_expr->kind == EXPR_UNARY_CAST_IMPLICIT) {
+       if (fmt_expr->kind == EXPR_UNARY_CAST) {
                fmt_expr = fmt_expr->unary.value;
        }
 
-       vchar_t vchar;
-       if (fmt_expr->kind == EXPR_WIDE_STRING_LITERAL) {
-               vchar.string   = &fmt_expr->wide_string.value;
-               vchar.size     = fmt_expr->wide_string.value.size;
-               vchar.first    = wstring_first;
-               vchar.next     = wstring_next;
-               vchar.is_digit = wstring_isdigit;
-       } else if (fmt_expr->kind == EXPR_STRING_LITERAL) {
-               vchar.string   = &fmt_expr->string.value;
-               vchar.size     = fmt_expr->string.value.size;
-               vchar.first    = string_first;
-               vchar.next     = string_next;
-               vchar.is_digit = string_isdigit;
-       } else {
+       if (fmt_expr->kind != EXPR_STRING_LITERAL)
                return;
-       }
+
+       const char *string = fmt_expr->string_literal.value.begin;
+       size_t      size   = fmt_expr->string_literal.value.size;
+       const char *c      = string;
+
        /* find the real args */
        for (; idx < spec->arg_idx && arg != NULL; ++idx)
                arg = arg->next;
 
-       const source_position_t *pos = &fmt_expr->base.source_position;
-       unsigned fmt     = vchar.first(&vchar);
+       const position_t *pos = &fmt_expr->base.pos;
        unsigned num_fmt = 0;
-       for (; fmt != '\0'; fmt = vchar.next(&vchar)) {
+       char     fmt;
+       for (fmt = *c; fmt != '\0'; fmt = *(++c)) {
                if (fmt != '%')
                        continue;
-               fmt = vchar.next(&vchar);
-
+               fmt = *(++c);
                if (fmt == '%')
                        continue;
 
                ++num_fmt;
 
-               /* length modifier */
-               format_length_modifier_t fmt_mod;
+               bool suppress_assignment = false;
+               if (fmt == '*') {
+                       fmt = *++c;
+                       suppress_assignment = true;
+               }
+
+               size_t width = 0;
+               if ('0' <= fmt && fmt <= '9') {
+                       do {
+                               width = width * 10 + (fmt - '0');
+                               fmt   = *++c;
+                       } while ('0' <= fmt && fmt <= '9');
+                       if (width == 0) {
+                               warningf(WARN_FORMAT, pos, "field width is zero at format %u", num_fmt);
+                       }
+               }
+
+               /* look for length modifiers */
+               format_length_modifier_t fmt_mod = FMT_MOD_NONE;
                switch (fmt) {
-                       case 'h':
-                               fmt = vchar.next(&vchar);
-                               if (fmt == 'h') {
-                                       fmt = vchar.next(&vchar);
-                                       fmt_mod = FMT_MOD_hh;
-                               } else {
-                                       fmt_mod = FMT_MOD_h;
-                               }
-                               break;
+               case 'h':
+                       fmt = *(++c);
+                       if (fmt == 'h') {
+                               fmt = *(++c);
+                               fmt_mod = FMT_MOD_hh;
+                       } else {
+                               fmt_mod = FMT_MOD_h;
+                       }
+                       break;
 
-                       case 'l':
-                               fmt = vchar.next(&vchar);
-                               if (fmt == 'l') {
-                                       fmt = vchar.next(&vchar);
-                                       fmt_mod = FMT_MOD_ll;
-                               } else {
-                                       fmt_mod = FMT_MOD_l;
-                               }
-                               break;
+               case 'l':
+                       fmt = *(++c);
+                       if (fmt == 'l') {
+                               fmt = *(++c);
+                               fmt_mod = FMT_MOD_ll;
+                       } else {
+                               fmt_mod = FMT_MOD_l;
+                       }
+                       break;
 
-                       case 'L': fmt = vchar.next(&vchar); fmt_mod = FMT_MOD_L;    break;
-                       case 'j': fmt = vchar.next(&vchar); fmt_mod = FMT_MOD_j;    break;
-                       case 't': fmt = vchar.next(&vchar); fmt_mod = FMT_MOD_t;    break;
-                       case 'z': fmt = vchar.next(&vchar); fmt_mod = FMT_MOD_z;    break;
-                       /* microsoft mode */
-                       case 'w':
-                               if (c_mode & _MS) {
-                                       fmt = vchar.next(&vchar); fmt_mod = FMT_MOD_w;
-                               } else {
-                                       fmt_mod = FMT_MOD_NONE;
-                               }
-                               break;
-                       case 'I':
-                               if (c_mode & _MS) {
-                                       fmt = vchar.next(&vchar); fmt_mod = FMT_MOD_I;
-                                       if (fmt == '3') {
-                                               fmt = vchar.next(&vchar);
-                                               if (fmt == '2') {
-                                                       fmt = vchar.next(&vchar);
-                                                       fmt_mod = FMT_MOD_I32;
-                                               } else {
-                                                       /* rewind */
-                                                       --vchar.position;
-                                               }
-                                       } else if (fmt == '6') {
-                                               fmt = vchar.next(&vchar);
-                                               if (fmt == '4') {
-                                                       fmt = vchar.next(&vchar);
-                                                       fmt_mod = FMT_MOD_I64;
-                                               } else {
-                                                       /* rewind */
-                                                       --vchar.position;
-                                               }
+               case 'L': fmt = *(++c); fmt_mod = FMT_MOD_L; break;
+               case 'j': fmt = *(++c); fmt_mod = FMT_MOD_j; break;
+               case 't': fmt = *(++c); fmt_mod = FMT_MOD_t; break;
+               case 'z': fmt = *(++c); fmt_mod = FMT_MOD_z; break;
+               /* microsoft mode */
+               case 'w':
+                       if (c_mode & _MS) {
+                               fmt = *(++c);
+                               fmt_mod = FMT_MOD_w;
+                       }
+                       break;
+               case 'I':
+                       if (c_mode & _MS) {
+                               fmt = *(++c);
+                               fmt_mod = FMT_MOD_I;
+                               if (fmt == '3') {
+                                       fmt = *(++c);
+                                       if (fmt == '2') {
+                                               fmt = *(++c);
+                                               fmt_mod = FMT_MOD_I32;
+                                       } else {
+                                               /* rewind */
+                                               fmt = *(--c);
+                                       }
+                               } else if (fmt == '6') {
+                                       fmt = *(++c);
+                                       if (fmt == '4') {
+                                               fmt = *(++c);
+                                               fmt_mod = FMT_MOD_I64;
+                                       } else {
+                                               /* rewind */
+                                               fmt = *(--c);
                                        }
-                               } else {
-                                       fmt_mod = FMT_MOD_NONE;
                                }
-                               break;
-                       default:
-                               fmt_mod = FMT_MOD_NONE;
-                               break;
+                       }
+                       break;
                }
 
                if (fmt == '\0') {
-                       warningf(pos, "dangling %% in format string");
+                       warningf(WARN_FORMAT, pos, "dangling %% with conversion specififer in format string");
                        break;
                }
 
-               type_t            *expected_type;
+               type_t *expected_type;
                switch (fmt) {
-                       case 'd':
-                       case 'i':
-                               switch (fmt_mod) {
-                                       case FMT_MOD_NONE: expected_type = type_int;         break;
-                                       case FMT_MOD_hh:   expected_type = type_signed_char; break;
-                                       case FMT_MOD_h:    expected_type = type_short;       break;
-                                       case FMT_MOD_l:    expected_type = type_long;        break;
-                                       case FMT_MOD_ll:   expected_type = type_long_long;   break;
-                                       case FMT_MOD_j:    expected_type = type_intmax_t;    break;
-                                       case FMT_MOD_z:    expected_type = type_ssize_t;     break;
-                                       case FMT_MOD_t:    expected_type = type_ptrdiff_t;   break;
-                                       case FMT_MOD_I:    expected_type = type_ptrdiff_t;   break;
-                                       case FMT_MOD_I32:  expected_type = type_int32;       break;
-                                       case FMT_MOD_I64:  expected_type = type_int64;       break;
+               case 'd':
+               case 'i':
+                       switch (fmt_mod) {
+                       case FMT_MOD_NONE: expected_type = type_int;         break;
+                       case FMT_MOD_hh:   expected_type = type_signed_char; break;
+                       case FMT_MOD_h:    expected_type = type_short;       break;
+                       case FMT_MOD_l:    expected_type = type_long;        break;
+                       case FMT_MOD_ll:   expected_type = type_long_long;   break;
+                       case FMT_MOD_j:    expected_type = type_intmax_t;    break;
+                       case FMT_MOD_z:    expected_type = type_ssize_t;     break;
+                       case FMT_MOD_t:    expected_type = type_ptrdiff_t;   break;
+                       case FMT_MOD_I:    expected_type = type_ptrdiff_t;   break;
+                       case FMT_MOD_I32:  expected_type = type_int32;       break;
+                       case FMT_MOD_I64:  expected_type = type_int64;       break;
 
-                                       default:
-                                               warn_invalid_length_modifier(pos, fmt_mod, fmt);
-                                               goto next_arg;
-                               }
-                               break;
+                       default:
+                               warn_invalid_length_modifier(pos, fmt_mod, fmt);
+                               goto next_arg;
+                       }
+                       break;
 
-                       case 'o':
-                       case 'X':
-                       case 'x':
-                               goto eval_fmt_mod_unsigned;
+               case 'o':
+               case 'X':
+               case 'x':
+               case 'u':
+                       switch (fmt_mod) {
+                       case FMT_MOD_NONE: expected_type = type_unsigned_int;       break;
+                       case FMT_MOD_hh:   expected_type = type_unsigned_char;      break;
+                       case FMT_MOD_h:    expected_type = type_unsigned_short;     break;
+                       case FMT_MOD_l:    expected_type = type_unsigned_long;      break;
+                       case FMT_MOD_ll:   expected_type = type_unsigned_long_long; break;
+                       case FMT_MOD_j:    expected_type = type_uintmax_t;          break;
+                       case FMT_MOD_z:    expected_type = type_size_t;             break;
+                       case FMT_MOD_t:    expected_type = type_uptrdiff_t;         break;
+                       case FMT_MOD_I:    expected_type = type_size_t;             break;
+                       case FMT_MOD_I32:  expected_type = type_unsigned_int32;     break;
+                       case FMT_MOD_I64:  expected_type = type_unsigned_int64;     break;
 
-                       case 'u':
-eval_fmt_mod_unsigned:
-                               switch (fmt_mod) {
-                                       case FMT_MOD_NONE: expected_type = type_unsigned_int;       break;
-                                       case FMT_MOD_hh:   expected_type = type_unsigned_char;      break;
-                                       case FMT_MOD_h:    expected_type = type_unsigned_short;     break;
-                                       case FMT_MOD_l:    expected_type = type_unsigned_long;      break;
-                                       case FMT_MOD_ll:   expected_type = type_unsigned_long_long; break;
-                                       case FMT_MOD_j:    expected_type = type_uintmax_t;          break;
-                                       case FMT_MOD_z:    expected_type = type_size_t;             break;
-                                       case FMT_MOD_t:    expected_type = type_uptrdiff_t;         break;
-                                       case FMT_MOD_I:    expected_type = type_size_t;             break;
-                                       case FMT_MOD_I32:  expected_type = type_unsigned_int32;     break;
-                                       case FMT_MOD_I64:  expected_type = type_unsigned_int64;     break;
-
-                                       default:
-                                               warn_invalid_length_modifier(pos, fmt_mod, fmt);
-                                               goto next_arg;
-                               }
-                               break;
+                       default:
+                               warn_invalid_length_modifier(pos, fmt_mod, fmt);
+                               goto next_arg;
+                       }
+                       break;
 
-                       case 'A':
-                       case 'a':
-                       case 'E':
-                       case 'e':
-                       case 'F':
-                       case 'f':
-                       case 'G':
-                       case 'g':
-                               switch (fmt_mod) {
-                                       case FMT_MOD_l:    /* l modifier is ignored */
-                                       case FMT_MOD_NONE: expected_type = type_double;      break;
-                                       case FMT_MOD_L:    expected_type = type_long_double; break;
+               case 'A':
+               case 'a':
+               case 'E':
+               case 'e':
+               case 'F':
+               case 'f':
+               case 'G':
+               case 'g':
+                       switch (fmt_mod) {
+                       case FMT_MOD_l:    expected_type = type_double;      break;
+                       case FMT_MOD_NONE: expected_type = type_float;       break;
+                       case FMT_MOD_L:    expected_type = type_long_double; break;
 
-                                       default:
-                                               warn_invalid_length_modifier(pos, fmt_mod, fmt);
-                                               goto next_arg;
-                               }
-                               break;
+                       default:
+                               warn_invalid_length_modifier(pos, fmt_mod, fmt);
+                               goto next_arg;
+                       }
+                       break;
 
-                       case 'C':
-                               if (fmt_mod != FMT_MOD_NONE) {
-                                       warn_invalid_length_modifier(pos, fmt_mod, fmt);
-                                       goto next_arg;
-                               }
-                               expected_type = type_wchar_t;
-                               break;
+               case 'C':
+                       if (fmt_mod != FMT_MOD_NONE) {
+                               warn_invalid_length_modifier(pos, fmt_mod, fmt);
+                               goto next_arg;
+                       }
+                       expected_type = type_wchar_t;
+                       goto check_c_width;
 
-                       case 'c':
-                               expected_type = type_int;
-                               switch (fmt_mod) {
-                                       case FMT_MOD_NONE: expected_type = type_int;     break; /* TODO promoted char */
-                                       case FMT_MOD_l:    expected_type = type_wint_t;  break;
-                                       case FMT_MOD_w:    expected_type = type_wchar_t; break;
+               case 'c': {
+                       switch (fmt_mod) {
+                       case FMT_MOD_NONE: expected_type = type_char;    break;
+                       case FMT_MOD_l:    expected_type = type_wchar_t; break;
+                       case FMT_MOD_w:    expected_type = type_wchar_t; break;
 
-                                       default:
-                                               warn_invalid_length_modifier(pos, fmt_mod, fmt);
-                                               goto next_arg;
-                               }
-                               break;
+                       default:
+                               warn_invalid_length_modifier(pos, fmt_mod, fmt);
+                               goto next_arg;
+                       }
 
-                       case 'S':
-                               if (fmt_mod != FMT_MOD_NONE) {
-                                       warn_invalid_length_modifier(pos, fmt_mod, fmt);
-                                       goto next_arg;
+check_c_width:
+                       if (width == 0)
+                               width = 1;
+                       if (!suppress_assignment && arg != NULL) {
+                               type_t *const type = skip_typeref(revert_automatic_type_conversion(arg->expression));
+                               if (is_type_array(type)       &&
+                                   type->array.size_constant &&
+                                   width > type->array.size) {
+                                       warningf(WARN_FORMAT, pos, "target buffer '%T' is too small for %u characters at format %u", type, width, num_fmt);
                                }
-                               expected_type = type_wchar_t;
-                               break;
+                       }
+                       break;
+               }
 
-                       case 's':
-                       case '[':
-                               switch (fmt_mod) {
-                                       case FMT_MOD_NONE: expected_type = type_char;    break;
-                                       case FMT_MOD_l:    expected_type = type_wchar_t; break;
-                                       case FMT_MOD_w:    expected_type = type_wchar_t; break;
+               case 'S':
+                       if (fmt_mod != FMT_MOD_NONE) {
+                               warn_invalid_length_modifier(pos, fmt_mod, fmt);
+                               goto next_arg;
+                       }
+                       expected_type = type_wchar_t;
+                       break;
 
-                                       default:
-                                               warn_invalid_length_modifier(pos, fmt_mod, fmt);
-                                               goto next_arg;
-                               }
-                               break;
+               case 's':
+               case '[': {
+                       switch (fmt_mod) {
+                               case FMT_MOD_NONE: expected_type = type_char;    break;
+                               case FMT_MOD_l:    expected_type = type_wchar_t; break;
+                               case FMT_MOD_w:    expected_type = type_wchar_t; break;
 
-                       case 'p':
-                               if (fmt_mod != FMT_MOD_NONE) {
+                               default:
                                        warn_invalid_length_modifier(pos, fmt_mod, fmt);
                                        goto next_arg;
+                       }
+
+                       if (!suppress_assignment &&
+                           width != 0           &&
+                           arg   != NULL) {
+                               type_t *const type = skip_typeref(revert_automatic_type_conversion(arg->expression));
+                               if (is_type_array(type)       &&
+                                   type->array.size_constant &&
+                                   width >= type->array.size) {
+                                       warningf(WARN_FORMAT, pos, "target buffer '%T' is too small for %u characters and \\0 at format %u", type, width, num_fmt);
                                }
-                               expected_type = type_void_ptr;
-                               break;
+                       }
+                       break;
+               }
 
-                       case 'n':
-                               switch (fmt_mod) {
-                                       case FMT_MOD_NONE: expected_type = type_int;         break;
-                                       case FMT_MOD_hh:   expected_type = type_signed_char; break;
-                                       case FMT_MOD_h:    expected_type = type_short;       break;
-                                       case FMT_MOD_l:    expected_type = type_long;        break;
-                                       case FMT_MOD_ll:   expected_type = type_long_long;   break;
-                                       case FMT_MOD_j:    expected_type = type_intmax_t;    break;
-                                       case FMT_MOD_z:    expected_type = type_ssize_t;     break;
-                                       case FMT_MOD_t:    expected_type = type_ptrdiff_t;   break;
+               case 'p':
+                       if (fmt_mod != FMT_MOD_NONE) {
+                               warn_invalid_length_modifier(pos, fmt_mod, fmt);
+                               goto next_arg;
+                       }
+                       expected_type = type_void;
+                       break;
 
-                                       default:
-                                               warn_invalid_length_modifier(pos, fmt_mod, fmt);
-                                               goto next_arg;
-                               }
-                               break;
+               case 'n': {
+                       if (suppress_assignment) {
+                               warningf(WARN_FORMAT, pos, "conversion '%n' cannot be suppressed with '*' at format %u", num_fmt);
+                       }
+
+                       switch (fmt_mod) {
+                       case FMT_MOD_NONE: expected_type = type_int;         break;
+                       case FMT_MOD_hh:   expected_type = type_signed_char; break;
+                       case FMT_MOD_h:    expected_type = type_short;       break;
+                       case FMT_MOD_l:    expected_type = type_long;        break;
+                       case FMT_MOD_ll:   expected_type = type_long_long;   break;
+                       case FMT_MOD_j:    expected_type = type_intmax_t;    break;
+                       case FMT_MOD_z:    expected_type = type_ssize_t;     break;
+                       case FMT_MOD_t:    expected_type = type_ptrdiff_t;   break;
 
                        default:
-                               warningf(pos, "encountered unknown conversion specifier '%%%C' at position %u", (wint_t)fmt, num_fmt);
-                               if (arg == NULL) {
-                                       warningf(pos, "too few arguments for format string");
-                                       return;
-                               }
+                               warn_invalid_length_modifier(pos, fmt_mod, fmt);
                                goto next_arg;
+                       }
+                       break;
+               }
+
+               default:
+                       warningf(WARN_FORMAT, pos, "encountered unknown conversion specifier '%%%c' at format %u", fmt, num_fmt);
+                       if (suppress_assignment)
+                               continue;
+                       if (arg == NULL)
+                               goto too_few_args;
+                       goto next_arg;
                }
 
+               if (suppress_assignment)
+                       continue;
+
                if (arg == NULL) {
-                       warningf(pos, "too few arguments for format string");
+too_few_args:
+                       warningf(WARN_FORMAT, pos, "too few arguments for format string");
                        return;
                }
 
-               {       /* create a scope here to prevent warning about the jump to next_arg */
+               { /* create a scope here to prevent warning about the jump to next_arg */
                        type_t *const arg_type           = arg->expression->base.type;
                        type_t *const arg_skip           = skip_typeref(arg_type);
                        type_t *const expected_type_skip = skip_typeref(expected_type);
@@ -901,16 +897,17 @@ eval_fmt_mod_unsigned:
                        }
 error_arg_type:
                        if (is_type_valid(arg_skip)) {
-                               warningf(pos,
-                                       "argument type '%T' does not match conversion specifier '%%%s%c' at position %u",
-                                       arg_type, get_length_modifier_name(fmt_mod), (char)fmt, num_fmt);
+                               position_t const *const apos = &arg->expression->base.pos;
+                               char       const *const mod  = get_length_modifier_name(fmt_mod);
+                               warningf(WARN_FORMAT, apos, "conversion '%%%s%c' at position %u specifies type '%T*' but the argument has type '%T'", mod, (char)fmt, num_fmt, expected_type, arg_type);
                        }
                }
 next_arg:
                arg = arg->next;
        }
-       if (!atend(&vchar)) {
-               warningf(pos, "format string contains '\\0'");
+       assert(fmt == '\0');
+       if (c+1 < string + size) {
+               warningf(WARN_FORMAT, pos, "format string contains '\\0'");
        }
        if (arg != NULL) {
                unsigned num_args = num_fmt;
@@ -918,9 +915,7 @@ next_arg:
                        ++num_args;
                        arg = arg->next;
                }
-               warningf(pos, "%u argument%s but only %u format specifier%s",
-                       num_args, num_args != 1 ? "s" : "",
-                       num_fmt, num_fmt != 1 ? "s" : "");
+               warningf(WARN_FORMAT, pos, "%u argument%s but only %u format specifier%s", num_args, num_args != 1 ? "s" : "", num_fmt, num_fmt != 1 ? "s" : "");
        }
 }
 
@@ -975,7 +970,7 @@ static const format_spec_t builtin_table[] = {
 
 void check_format(const call_expression_t *const call)
 {
-       if (!warning.format)
+       if (!is_warn_on(WARN_FORMAT))
                return;
 
        const expression_t *const func_expr = call->function;
@@ -985,30 +980,27 @@ void check_format(const call_expression_t *const call)
        const entity_t        *const entity = func_expr->reference.entity;
        const call_argument_t *      arg    = call->arguments;
 
-       if (false) {
-               /* the declaration has a GNU format attribute, check it */
-       } else {
-               /*
-                * For some functions we always check the format, even if it was not specified.
-                * This allows to check format even in MS mode or without header included.
-                */
-               const char *const name = entity->base.symbol->string;
-               for (size_t i = 0; i < lengthof(builtin_table); ++i) {
-                       if (strcmp(name, builtin_table[i].name) == 0) {
-                               switch (builtin_table[i].fmt_kind) {
-                               case FORMAT_PRINTF:
-                                       check_printf_format(arg, &builtin_table[i]);
-                                       break;
-                               case FORMAT_SCANF:
-                                       check_scanf_format(arg, &builtin_table[i]);
-                                       break;
-                               case FORMAT_STRFTIME:
-                               case FORMAT_STRFMON:
-                                       /* TODO: implement other cases */
-                                       break;
-                               }
+       /*
+        * For some functions we always check the format, even if it was not
+        * specified. This allows to check format even in MS mode or without
+        * header included.
+        */
+       const char *const name = entity->base.symbol->string;
+       for (size_t i = 0; i < lengthof(builtin_table); ++i) {
+               if (streq(name, builtin_table[i].name)) {
+                       switch (builtin_table[i].fmt_kind) {
+                       case FORMAT_PRINTF:
+                               check_printf_format(arg, &builtin_table[i]);
+                               break;
+                       case FORMAT_SCANF:
+                               check_scanf_format(arg, &builtin_table[i]);
+                               break;
+                       case FORMAT_STRFTIME:
+                       case FORMAT_STRFMON:
+                               /* TODO: implement other cases */
                                break;
                        }
+                       break;
                }
        }
 }