add notes about const/pure properties and inifite loops

diff --git a/include/libfirm/firm_types.h b/include/libfirm/firm_types.h
index cbd7826..3c3657e 100644 (file)
--- a/include/libfirm/firm_types.h
+++ b/include/libfirm/firm_types.h
@@ -179,10 +179,17 @@ typedef enum mtp_additional_properties {
        mtp_no_property            = 0x00000000, /**< no additional properties, default */
        mtp_property_const         = 0x00000001, /**< This method did not access memory and calculates
                                                      its return values solely from its parameters.
+                                                     The only observable effect of a const function must be its
+                                                     return value. So they must not exhibit infinite loops or wait
+                                                     for user input. The return value must not depend on any
+                                                     global variables/state.
                                                      GCC: __attribute__((const)). */
        mtp_property_pure          = 0x00000002, /**< This method did NOT write to memory and calculates
                                                      its return values solely from its parameters and
                                                      the memory they points to (or global vars).
+                                                     The only observable effect of a const function must be its
+                                                     return value. So they must not exhibit infinite loops or wait
+                                                     for user input.
                                                      GCC: __attribute__((pure)). */
        mtp_property_noreturn      = 0x00000004, /**< This method did not return due to an aborting system
                                                      call.