为什么在 Windows 上使用 dirent.h 时出现类型不完整的错误？

Question

I have a C project that combines multiple.c and.h files. Previously I just had all of these files in the top level directory, along with the following Makefile:

O = o
E =
CC = gcc
OUT = cusum$E
CFLAGS = -D_GNU_SOURCE -O3 -Wall -Wextra --static
DEPS = bessel.h detector.h io.h stepfit.h lmmin_int64.h utils.h
ODIR = obj
_OBJ = main.$O bessel.$O detector.$O io.$O lmmin_int64.$O stepfit.$O utils.$O
OBJ = $(patsubst %,$(ODIR)/%,$(_OBJ))
LIBS = -lm

$(ODIR)/%.$O: %.c $(DEPS)
    $(CC) -c -o $@ $< $(CFLAGS) $(LIBS)

$(OUT): $(OBJ)
    $(CC) -o $@ $^ $(CFLAGS) $(LIBS)

.PHONY: clean win

clean:
    rm -f $(OUT) $(ODIR)/*.$O *~ core $(INCDIR)/*~
    rm -f $(OUT).exe w$(ODIR)/*.obj *~ core $(INCDIR)/*~

win:
    $(MAKE) CC=x86_64-w64-mingw32-gcc E=.exe O=obj ODIR=wobj

This works fine as far as I can tell.

I then reorganized things, putting the .c files in a src folder and the .h files in a lib folder. I changed the Makefile to the following:

O = o
E =
CC = gcc
OUT = dist/cusum$E
CFLAGS = -D_GNU_SOURCE -O3 -Wall -Wextra --static
INCDIR = lib/
DEPS = lib/*.h
ODIR = build/obj
_OBJ = main.$O bessel.$O detector.$O io.$O lmmin_int64.$O stepfit.$O utils.$O
OBJ = $(patsubst %,$(ODIR)/%,$(_OBJ))
LIBS = -lm

$(ODIR)/%.$O: src/%.c $(DEPS)
    $(CC) -c -o $@ $< $(CFLAGS) -I$(INCDIR) $(LIBS)

$(OUT): $(OBJ)
    $(CC) -o $@ $^ $(CFLAGS) -I$(INCDIR) $(LIBS)

.PHONY: clean win cleanwin

clean:
    rm -f $(OUT) $(ODIR)/*.$(O) *~ core $(INCDIR)/*~

win:
    $(MAKE) CC=x86_64-w64-mingw32-gcc E=.exe O=obj ODIR=build/wobj
    
cleanwin:
    $(MAKE) clean CC=x86_64-w64-mingw32-gcc E=.exe O=obj ODIR=build/wobj

Now, when I compile for Linux ( make ), it works OK. When I cross-compile for windows ( make win ), I get the following error:

`make[1]: Entering directory '[...]'

x86_64-w64-mingw32-gcc -c -o build/wobj/main.obj src/main.c -D_GNU_SOURCE -O3 -Wall -Wextra --static -Ilib/ -lm

In file included from lib/io.h:31:0,
                 from src/main.c:21:

/usr/share/mingw-w64/include/dirent.h:41:21: error: field ‘dd_dta’ has incomplete type
  struct _finddata_t dd_dta;
                     ^~~~~~

/usr/share/mingw-w64/include/dirent.h:88:22: error: field ‘dd_dta’ has incomplete type
  struct _wfinddata_t dd_dta;

`

main.c includes all the libraries via:

#include"lib1.h"
#include"lib2.h"
....

and is located in the src folder

If I return the folder structure to what it was before and use the old Makefile, it works and tests fine, so I think the issue lies in the Makefile rather than the code itself. Can anyone point me in the right direction? If any information is missing, please let me know so I can fix it.

Answer 1

So it seems that the windows version of MinGW has some definition issues. The following code added to my compiler's version of include/dirent.h fixed the problem for me. Editing library functions is probably a bad idea generally, so only use this if you're feeling adventurous... I make no claims that this won't break all the things elsewhere.

#ifndef _FSIZE_T_DEFINED
typedef unsigned long   _fsize_t;
#define _FSIZE_T_DEFINED
#endif

struct _finddata_t
{
    unsigned    attrib;     /* Attributes, see constants above. */
    time_t      time_create;
    time_t      time_access;    /* always midnight local time */
    time_t      time_write;
    _fsize_t    size;
    char        name[FILENAME_MAX]; /* may include spaces. */
};

struct _wfinddata_t
{
    unsigned    attrib;     /* Attributes, see constants above. */
    time_t      time_create;
    time_t      time_access;    /* always midnight local time */
    time_t      time_write;
    size_t  size;
    wchar_t     name[FILENAME_MAX]; /* may include spaces. */
};