#2794 Windows : winmain.c fails to be complied

[Tatsuro MATSUOKA]

In the git repository, windows build fails.

gcc -c -m64 -O2 -pipe -DUNICODE -D_UNICODE -Wno-unused-function -DGNUPLOT_PS_DIR=\"share/PostScript\" -I. -I../../src -I../../term/ -DHAVE_CONFIG_H -D__USE_MINGW_ANSI_STDIO=1 -DWITH_CHI_SHAPES=1 -DGNUPLOT_SHARE_DIR=\"share\" -DDEVELOPMENT_VERSION -DUSE_MOUSE=1 -DWIN_IPC -I/c/Program\ Files\ (x86)/HTML\ Help\ Workshop/include -DHAVE_LIBGD -DHAVE_LIBPNG -DHAVE_LIBGD -DHAVE_GD_H -DHAVE_GD_GIF -DGIF_ANIMATION -DHAVE_GD_PNG -IC:/Programs/msys64/mingw64/include/X11 -IC:/Programs/msys64/mingw64/include/webp -DLIBDEFLATE_DLL -IC:/Programs/msys64/mingw64/include/freetype2 -IC:/Programs/msys64/mingw64/include/libpng16 -IC:/Programs/msys64/mingw64/include/harfbuzz -IC:/Programs/msys64/mingw64/include/glib-2.0 -IC:/Programs/msys64/mingw64/lib/glib-2.0/include -DHAVE_GD_JPEG -DHAVE_GD_TTF -DHAVE_CAIROPDF -DHAVE_WEBP -DWXWIDGETS -DQTTERM -DQT_NO_OPENGL -DHAVE_LUA -DHAVE_ICONV -DHAVE_LIBCERF -DNEED_CEXP -DHAVE_AMOS -DREADLINE -DUSE_WATCHPOINTS -DUSE_POLAR_GRID -DUSE_FUNCTIONBLOCKS -DWITH_STABLE_SORT -DHAVE_D2D11 -DPIPES -MMD -MT 'winmain.o' -MF winmain.d -o winmain.o ../../src/win/winmain.c
../../src/win/winmain.c: In function 'appdata_directory':
../../src/win/winmain.c:287:14: error: too many arguments to function 'pSHGetSpecialFolderPath'; expected 0, have 4
287 | (*pSHGetSpecialFolderPath)(NULL, dir, CSIDL_APPDATA, FALSE);
| ~^~~~~~~~~~~~~~~~~~~~~~~~~ ~~~~
make: *** [Makefile:679: winmain.o] Error 1

[Ethan Merritt]

Is it possible you have a new C compiler?

The very recent gcc15 release has made a number of issues that used to be warnings into errors instead. This is apparently because of stricter requirements in the C23 standard. So if the error is from gcc15 you might be able to avoid it by adding the compiler flag -std=gnu17

Or they might fix this in gcc. See
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=118112

[Tatsuro MATSUOKA]

Addtion of -std=gnu17 option to CFLAGS eliminates the issue.
Thanks!

[Ethan Merritt]

Based on this Microsoft page
https://learn.microsoft.com/en-us/cpp/build/getprocaddress?view=msvc-170
I think the correct fix is to provide a full prototype for the function.
Can you test the attached patch?

[Tatsuro MATSUOKA]

Testted but an error appears

gcc -c -m64 -O2 -pipe -DUNICODE -D_UNICODE -Wno-unused-function -DGNUPLOT_PS_DIR=\"share/PostScript\"  -I. -I../../src -I../../term/ -DHAVE_CONFIG_H -D__USE_MINGW_ANSI_STDIO=1 -DWITH_CHI_SHAPES=1 -DGNUPLOT_SHARE_DIR=\"share\" -DDEVELOPMENT_VERSION -DUSE_MOUSE=1 -DWIN_IPC -I/c/Program\ Files\ \(x86\)/HTML\ Help\ Workshop/include -DHAVE_LIBGD -DHAVE_LIBPNG -DHAVE_LIBGD -DHAVE_GD_H -DHAVE_GD_GIF -DGIF_ANIMATION -DHAVE_GD_PNG -IC:/Programs/msys64/mingw64/include/X11 -IC:/Programs/msys64/mingw64/include/webp -DLIBDEFLATE_DLL -IC:/Programs/msys64/mingw64/include/freetype2 -IC:/Programs/msys64/mingw64/include/libpng16 -IC:/Programs/msys64/mingw64/include/harfbuzz -IC:/Programs/msys64/mingw64/include/glib-2.0 -IC:/Programs/msys64/mingw64/lib/glib-2.0/include -DHAVE_GD_JPEG -DHAVE_GD_TTF -DHAVE_CAIROPDF -DHAVE_WEBP -DWXWIDGETS -DQTTERM -DQT_NO_OPENGL -DHAVE_LUA -DHAVE_ICONV -DHAVE_LIBCERF -DNEED_CEXP -DHAVE_AMOS -DREADLINE -DUSE_WATCHPOINTS -DUSE_POLAR_GRID -DUSE_FUNCTIONBLOCKS -DWITH_STABLE_SORT -DHAVE_D2D11 -DPIPES -MMD -MT 'winmain.o' -MF winmain.d -o winmain.o ../../src/win/winmain.c
../../src/win/winmain.c: In function 'appdata_directory':
../../src/win/winmain.c:279:17: error: redefinition of 'dir'
  279 |     static char dir[MAX_PATH] = "";
      |                 ^~~
../../src/win/winmain.c:277:18: note: previous definition of 'dir' with type 'char[260]'
  277 |      static char dir[MAX_PATH] = "";
      |                  ^~~
../../src/win/winmain.c:289:33: error: assignment to 'GETFOLDERPATH' {aka 'unsigned int (*)(struct HWND__ *, char *, int,  int)'} from incompatible pointer type 'FARPROC' {aka 'long long int (*)(void)'} [-Wincompatible-pointer-types]
  289 |         pSHGetSpecialFolderPath =
      |                                 ^
../../src/win/winmain.c:274:29: note: 'GETFOLDERPATH' declared here
  274 |     typedef UINT (CALLBACK* GETFOLDERPATH)
      |                             ^~~~~~~~~~~~~
In file included from C:/Programs/msys64/mingw64/include/windef.h:9,
                 from C:/Programs/msys64/mingw64/include/windows.h:69,
                 from ../../src/win/winmain.c:50:
C:/Programs/msys64/mingw64/include/minwindef.h:196:28: note: 'FARPROC' declared here
  196 |   typedef INT_PTR (WINAPI *FARPROC) ();
      |                            ^~~~~~~
make: *** [Makefile:679: winmain.o] Error 1

[Ethan Merritt]

Ugh. One more try. If this one doesn't work I will have to leave it to someone more familiar with Windows programming.

[Tatsuro MATSUOKA]

The 2nd patch solves the issue. Thanks!