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file_win32: fix UB when preparing args for CreateFileMappingA #113

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file_win32: fix UB when preparing args for CreateFileMappingA #113

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15 changes: 13 additions & 2 deletions src/cio_file_win32.c
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Original file line number Diff line number Diff line change
Expand Up @@ -18,6 +18,7 @@
*/

#include <inttypes.h>
#include <limits.h>
#include <stdio.h>

#include <chunkio/chunkio_compat.h>
Expand Down Expand Up @@ -76,6 +77,8 @@ int cio_file_native_map(struct cio_file *cf, size_t map_size)
DWORD desired_access;
size_t file_size;
size_t actual_map_size;
DWORD actual_map_size_high;
DWORD actual_map_size_low;
int ret;

if (cf == NULL) {
Expand Down Expand Up @@ -131,10 +134,18 @@ int cio_file_native_map(struct cio_file *cf, size_t map_size)

/* CreateFileMappingA requires size as two DWORDs (high and low) */
/* Use actual_map_size to ensure consistency */
#if SIZE_MAX > MAXDWORD
actual_map_size_high = (DWORD)((actual_map_size >> (sizeof(DWORD) * CHAR_BIT))
& 0xFFFFFFFFUL);
actual_map_size_low = (DWORD)(actual_map_size & 0xFFFFFFFFUL);
#else
actual_map_size_high = 0;
actual_map_size_low = (DWORD)actual_map_size;
#endif
cf->backing_mapping = CreateFileMappingA(cf->backing_file, NULL,
desired_protection,
(DWORD)(actual_map_size >> 32),
(DWORD)(actual_map_size & 0xFFFFFFFFUL),
actual_map_size_high,
actual_map_size_low,
NULL);

if (cf->backing_mapping == NULL) {
Expand Down
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