`strdup` missing `dllimport` declaration (Windows)

[vikhik]

Running clang-tidy with a reasonably "default" (based on llvm) set of checks on the clear renderer sample gives this:

D:/dev/proj/build/Windows/_deps/sdl3-src/include\SDL3/SDL_stdinc.h:5966:7: error: 'strdup' redeclared without 'dllimport' attribute: previous 'dllimport' ignored [clang-diagnostic-inconsistent-dllimport]
 5966 | char *strdup(const char *str);
      |       ^
C:\Program Files (x86)\Windows Kits\10\Include\10.0.26100.0\ucrt\string.h:532:28: note: previous declaration is here
  532 |     _ACRTIMP char* __cdecl strdup(
      |                            ^
C:\Program Files (x86)\Windows Kits\10\Include\10.0.26100.0\ucrt\string.h:532:5: note: previous attribute is here
  532 |     _ACRTIMP char* __cdecl strdup(
      |     ^
C:\Program Files (x86)\Windows Kits\10\Include\10.0.26100.0\ucrt\corecrt.h:136:37: note: expanded from macro '_ACRTIMP'
  136 |         #define _ACRTIMP __declspec(dllimport)
      |                                     ^

[madebr]

SDL/include/SDL3/SDL_stdinc.h

Lines 5955 to 6023 in 15c6acf

	/* force builds using Clang's static analysis tools to use literal C runtime
	here, since there are possibly tests that are ineffective otherwise. */
	#if defined(__clang_analyzer__) && !defined(SDL_DISABLE_ANALYZE_MACROS)
	/* The analyzer knows about strlcpy even when the system doesn't provide it */
	#if !defined(HAVE_STRLCPY) && !defined(strlcpy)
	size_t strlcpy(char *dst, const char *src, size_t size);
	#endif
	/* The analyzer knows about strlcat even when the system doesn't provide it */
	#if !defined(HAVE_STRLCAT) && !defined(strlcat)
	size_t strlcat(char *dst, const char *src, size_t size);
	#endif
	#if !defined(HAVE_WCSLCPY) && !defined(wcslcpy)
	size_t wcslcpy(wchar_t *dst, const wchar_t *src, size_t size);
	#endif
	#if !defined(HAVE_WCSLCAT) && !defined(wcslcat)
	size_t wcslcat(wchar_t *dst, const wchar_t *src, size_t size);
	#endif
	/* strdup is not ANSI but POSIX, and its prototype might be hidden... */
	char *strdup(const char *str);
	/* Starting LLVM 16, the analyser errors out if these functions do not have
	their prototype defined (clang-diagnostic-implicit-function-declaration) */
	#include <stdio.h>
	#include <stdlib.h>
	#define SDL_malloc malloc
	#define SDL_calloc calloc
	#define SDL_realloc realloc
	#define SDL_free free
	#ifndef SDL_memcpy
	#define SDL_memcpy memcpy
	#endif
	#ifndef SDL_memmove
	#define SDL_memmove memmove
	#endif
	#ifndef SDL_memset
	#define SDL_memset memset
	#endif
	#define SDL_memcmp memcmp
	#define SDL_strlcpy strlcpy
	#define SDL_strlcat strlcat
	#define SDL_strlen strlen
	#define SDL_wcslen wcslen
	#define SDL_wcslcpy wcslcpy
	#define SDL_wcslcat wcslcat
	#define SDL_strdup strdup
	#define SDL_wcsdup wcsdup
	#define SDL_strchr strchr
	#define SDL_strrchr strrchr
	#define SDL_strstr strstr
	#define SDL_wcsstr wcsstr
	#define SDL_strtok_r strtok_r
	#define SDL_strcmp strcmp
	#define SDL_wcscmp wcscmp
	#define SDL_strncmp strncmp
	#define SDL_wcsncmp wcsncmp
	#define SDL_strcasecmp strcasecmp
	#define SDL_strncasecmp strncasecmp
	#define SDL_strpbrk strpbrk
	#define SDL_sscanf sscanf
	#define SDL_vsscanf vsscanf
	#define SDL_snprintf snprintf
	#define SDL_vsnprintf vsnprintf
	#endif

I'd remove our declarations and do #include <string.h> when using __clang_analyzer__.
What do you think @sezero?

[sezero]

string.h is already included, as the error message shows. The problem is with our prototype, which was added to fix #11219, conflicting with the one in string.h.

[sezero]

One thing I can think of is removing our proto, but defining prerequite macros (_GNU_SOURCE? __POSIX_C_SOURCE?? whatever) to ensure strdup prototype is visible from string.h when in clang-analyzer mode.

[sezero]

One thing I can think of is removing our proto, but defining prerequite macros (_GNU_SOURCE? __POSIX_C_SOURCE?? whatever) to ensure strdup prototype is visible from string.h when in clang-analyzer mode.

Thinking about it, that would require definig the necessary macro(s) before including any system headers, just because of this.

How about just guarding our prototype simply with #ifndef _WIN32 ?

[madebr]

How about just guarding our prototype simply with #ifndef _WIN32 ?

That seems fine to me. (I don't understand the problem well enough.)

From #11219 (comment), @Sackzement was also running into this problem. Would this fix the problem for you too? (without needing a SDL_DISABLE_ANALYZE_MACROS macro)

[sezero]

Pull request: #12951