unity_fixture.c compiler warning with optimizations turned on

When I compile unity_fixture.c with gcc 4.4.3 and -O0, it compiles cleanly. However, when I compile it with -O1 or greater, I get the following warning:

gcc -IUnity/src -IUnity/extras/fixture/src -O1 -c Unity/extras/fixture/src/unity_fixture.c -o test/build/unity_fixture.o
Unity/extras/fixture/src/unity_fixture.c: In function ‘unity_malloc’:
Unity/extras/fixture/src/unity_fixture.c:202: warning: incompatible implicit declaration of built-in function ‘malloc'

unity_fixture.c includes <stdlib.h> before any reference to malloc, so I can’t see why this would be happening, let alone only happening at some optimization levels.

It’s causing trouble for me because I’d like to use -Werror on my builds.

I’ve tracked this bug down. The short answer is, unity_fixture.c should include string.h before unity_fixture.h.

It seems that string.h on Linux may include a minimal stdlib.h which includes definitions for malloc and calloc (see bits/string2.h and the macro __need_malloc_and_calloc).

Since unity_fixture.h is included in unity_fixture.c before string.h, a preprocessor definition of malloc -> unity_malloc exists when string.h includes stdlib.h, and stdlib.h accidentally emits a prototype for a function named unity_malloc instead of one named malloc. stdlib.h also sets __malloc_and_calloc_defined so that it doesn’t try to define those functions twice, so the later explicit including of stdlib.h doesn’t get us the malloc and calloc prototypes we want.

phew.

I got the fix for this bug merged upstream. Details here:

https://github.com/ThrowTheSwitch/Unity/pull/25