fix UWP build

[robUx4]

BY_HANDLE_FILE_INFORMATION is not defined when WINSTORECOMPAT is not defined (in mingw-w64 and never in MSVC).

follow up to 7dfcd73

[sezero]

With plain mingw build, I get:

  CC       grabbag/file.lo
../../../src/share/grabbag/file.c: In function 'grabbag__file_are_same':
../../../src/share/grabbag/file.c:147:2: warning: ISO C90 forbids mixed declarations and code
  CCLD     grabbag/libgrabbag.la

Maybe enclose the info1|2 stuff in braces to avoid that?

[sezero]

Also, there seems to be an else missing in there because the info1|2 stuff are supposed to work only on valid handles.

I suggest something like the following, on top of your patch. (formatting excluded deliberately.)

diff --git a/src/share/grabbag/file.c b/src/share/grabbag/file.c
index 652ef70..d20f9b8 100644
--- a/src/share/grabbag/file.c
+++ b/src/share/grabbag/file.c
@@ -143,6 +143,8 @@ FLAC__bool grabbag__file_are_same(const char *f1, const char *f2)
 	h2 = CreateFile_utf8(f2, GENERIC_READ, FILE_SHARE_READ, NULL, OPEN_EXISTING, FILE_ATTRIBUTE_NORMAL, NULL);
 	if(h1 == INVALID_HANDLE_VALUE || h2 == INVALID_HANDLE_VALUE)
 		ok = 0;
+	else
+	{
 #if WINAPI_FAMILY_PARTITION(WINAPI_PARTITION_DESKTOP)
 	BY_HANDLE_FILE_INFORMATION info1, info2;
 	ok &= GetFileInformationByHandle(h1, &info1);
@@ -159,7 +161,9 @@ FLAC__bool grabbag__file_are_same(const char *f1, const char *f2)
 	       GetFileInformationByHandleEx(h2, FileIdInfo, &id_info2, sizeof (id_info2)) &&
 	       id_info1.VolumeSerialNumber == id_info2.VolumeSerialNumber &&
 	       memcmp(&id_info1.FileId, &id_info2.FileId, sizeof(id_info1.FileId)) == 0;
+
 #endif // !WINAPI_PARTITION_DESKTOP
+	}
 	if(h1 != INVALID_HANDLE_VALUE)
 		CloseHandle(h1);
 	if(h2 != INVALID_HANDLE_VALUE)

[robUx4]

With plain mingw build, I get:

  CC       grabbag/file.lo
../../../src/share/grabbag/file.c: In function 'grabbag__file_are_same':
../../../src/share/grabbag/file.c:147:2: warning: ISO C90 forbids mixed declarations and code
  CCLD     grabbag/libgrabbag.la

Maybe enclose the info1|2 stuff in braces to avoid that?

Sure it's possible, but it's just a warning. Any modern C compiler (including that one) understands this. I can completely refactor the code to support C89 or K&R C, but is that really supposed to be supported when targeting Windows ? I can understand it may be needed for some embedded platform, but I doubt it on Windows. Is there a minimum requirement for the C standard supported ? There doesn't seem to be any set in the autoconf or CMake files.

The configure.ac says this:

#Prefer whatever the current ISO standard is.
AC_PROG_CC

[robUx4]

Also, there seems to be an else missing in there because the info1|2 stuff are supposed to work only on valid handles.

What makes you think that ? The documentation doesn't say that:

• https://learn.microsoft.com/en-us/windows/win32/api/fileapi/nf-fileapi-getfileinformationbyhandle
• https://learn.microsoft.com/en-us/windows/win32/api/winbase/nf-winbase-getfileinformationbyhandleex

And this code executes just fine and return FALSE on both case:

    BY_HANDLE_FILE_INFORMATION old;
    BOOL old_ret = GetFileInformationByHandle(INVALID_HANDLE_VALUE, &old);
    FILE_BASIC_INFO new;
    BOOL new_ret = GetFileInformationByHandleEx(INVALID_HANDLE_VALUE, FileBasicInfo, &new, sizeof(new));

Also this is out of the scope of what this MR is fixing.

[robUx4]

Closing this as it's an issue in mingw-w64 and not really a FLAC issue (see #612).

[robUx4]

BTW this line in a public header says it assumes that C99 headers are present:

flac/include/FLAC/ordinals.h

Line 36 in 6571cbb

/* This of course assumes C99 headers */

It would be a good idea to set that minimum in the CMake and autotools projects.

[ktmf01]

Here is some discussion about supporting C89 with some C99 headers: #483 I'd like to keep the assumptions about C standard version as compatible as possible (within reason) as libFLAC is used in quite a few embedded applications as well. In that case, that means C89, with the exception of some headers. stdint.h and stdbool.h shouldn't be too hard to "emulate".

FWIW I also think it is good practice (or at least part of the coding style) to not mix declarations and code.

[robUx4]

If you want to make sure this compatibility doesn't break, you should enforce it in CMake with set(CMAKE_C_STANDARD 90). Or at least in the CI with -DCMAKE_C_STANDARD=90.