X-Git-Url: http://nsz.repo.hu/git/?a=blobdiff_plain;f=format_check.c;h=359a7163df2e1e1ab7c200c65c908345eb32a177;hb=8845feb009950d2c76a394660a5bd81a0be0f2a6;hp=e33b0be5d5fb6e541d6ce13ae7ff962514388463;hpb=6d7d61de445629e1590d3a2ba2990ef7a651368a;p=cparser

diff --git a/format_check.c b/format_check.c
index e33b0be..359a716 100644
--- a/format_check.c
+++ b/format_check.c
@@ -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 utf32 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;
 		}
 	}
 }