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authorVadim Zeitlin <vadim@zeitlins.org>2019-10-06 01:47:06 +0200
committerVadim Zeitlin <vadim@zeitlins.org>2019-10-06 01:50:33 +0200
commitcad76c5b089d44dd0a0e17cc67de9da93c5655af (patch)
tree874f22fda8794bdbbbbe35671a314bfd160cf3cf
parent43b0c984f0a2c81565b05b6590bf9de7df612477 (diff)
downloadlibtiff-git-cad76c5b089d44dd0a0e17cc67de9da93c5655af.tar.gz
Avoid warnings about casts between HANDLE and int in Win64 builds
Add helper thandle_{from,to}_int() functions performing the casts between (64-bit, under Win64) thandle_t and (32-bit, always) int in a way that doesn't trigger compiler warnings. Also explain why suppressing these warnings is the right thing to do. Closes https://gitlab.com/libtiff/libtiff/issues/2
-rw-r--r--libtiff/tif_win32.c50
1 files changed, 27 insertions, 23 deletions
diff --git a/libtiff/tif_win32.c b/libtiff/tif_win32.c
index 088880e7..bf5fbfb3 100644
--- a/libtiff/tif_win32.c
+++ b/libtiff/tif_win32.c
@@ -27,33 +27,37 @@
* Scott Wagner (wagner@itek.com), Itek Graphix, Rochester, NY USA
*/
-/*
- CreateFileA/CreateFileW return type 'HANDLE'.
-
- thandle_t is declared like
-
- DECLARE_HANDLE(thandle_t);
+#include "tiffiop.h"
- in tiffio.h.
+#include <windows.h>
- Windows (from winnt.h) DECLARE_HANDLE logic looks like
+/*
+ CreateFileA/CreateFileW return type 'HANDLE' while TIFFFdOpen() takes 'int',
+ which is formally incompatible and can even seemingly be of different size:
+ HANDLE is 64 bit under Win64, while int is still 32 bits there.
- #ifdef STRICT
- typedef void *HANDLE;
- #define DECLARE_HANDLE(name) struct name##__ { int unused; }; typedef struct name##__ *name
- #else
- typedef PVOID HANDLE;
- #define DECLARE_HANDLE(name) typedef HANDLE name
- #endif
+ However, only the lower 32 bits of a HANDLE are significant under Win64 as,
+ for interoperability reasons, they must have the same values in 32- and
+ 64-bit programs running on the same system, see
- See http://bugzilla.maptools.org/show_bug.cgi?id=1941 for problems in WIN64
- builds resulting from this. Unfortunately, the proposed patch was lost.
+ https://docs.microsoft.com/en-us/windows/win32/winprog64/interprocess-communication
+ Because of this, it is safe to define the following trivial functions for
+ casting between ints and HANDLEs, which are only really needed to avoid
+ compiler warnings (and, perhaps, to make the code slightly more clear).
+ Note that using the intermediate cast to "intptr_t" is crucial for warning
+ avoidance, as this integer type has the same size as HANDLE in all builds.
*/
-
-#include "tiffiop.h"
-#include <windows.h>
+static inline thandle_t thandle_from_int(int ifd)
+{
+ return (thandle_t)(intptr_t)ifd;
+}
+
+static inline int thandle_to_int(thandle_t fd)
+{
+ return (int)(intptr_t)fd;
+}
static tmsize_t
_tiffReadProc(thandle_t fd, void* buf, tmsize_t size)
@@ -237,7 +241,7 @@ TIFFFdOpen(int ifd, const char* name, const char* mode)
break;
}
}
- tif = TIFFClientOpen(name, mode, (thandle_t)ifd, /* FIXME: WIN64 cast to pointer warning */
+ tif = TIFFClientOpen(name, mode, thandle_from_int(ifd),
_tiffReadProc, _tiffWriteProc,
_tiffSeekProc, _tiffCloseProc, _tiffSizeProc,
fSuppressMap ? _tiffDummyMapProc : _tiffMapProc,
@@ -282,7 +286,7 @@ TIFFOpen(const char* name, const char* mode)
return ((TIFF *)0);
}
- tif = TIFFFdOpen((int)fd, name, mode); /* FIXME: WIN64 cast from pointer to int warning */
+ tif = TIFFFdOpen(thandle_to_int(fd), name, mode);
if(!tif)
CloseHandle(fd);
return tif;
@@ -337,7 +341,7 @@ TIFFOpenW(const wchar_t* name, const char* mode)
NULL, NULL);
}
- tif = TIFFFdOpen((int)fd, /* FIXME: WIN64 cast from pointer to int warning */
+ tif = TIFFFdOpen(thandle_to_int(fd),
(mbname != NULL) ? mbname : "<unknown>", mode);
if(!tif)
CloseHandle(fd);