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authorPádraig Brady <P@draigBrady.com>2014-10-08 12:35:36 +0100
committerPádraig Brady <P@draigBrady.com>2014-10-08 12:48:51 +0100
commit16c7267d7425fe59b6919e77fa572d104d72c2bf (patch)
treec3801552e2f534e5ac80f2a0151d37f9403b59f9
parentfcbbf1cdb8cf65cdbb47522e9e7eefcbe752406e (diff)
downloadcoreutils-16c7267d7425fe59b6919e77fa572d104d72c2bf.tar.xz
maint: avoid new signed overflow warning on 32 bit
Prompted by http://hydra.nixos.org/build/15682577 with GCC 4.8.3 on i686 src/tac.c:557:6: error: assuming signed overflow does not occur when simplifying conditional to constant [-Werror=strict-overflow] if (bytes_copied < 0) This happens because copy_to_temp() is inlined in tac_nonseekable(), thus reducing the comparison to the bytes_copied variable in copy_to_temp. Now this can't overflow on either 32 or 64 bit due to the protection of the preceding fwrite(). We could use a guard like "if (bytes_copied <= OFF_T_MAX - bytes_read)" to avoid the warning, but rather than a runtime branch, just use an unsigned type to avoid apparent signed overflow on systems where the accumulation is not promoted to unsigned (32 bit size_t, 64 bit off_t). * src/tac.c (copy_to_temp): Increment an unsigned type to avoid the subsequent signed overflow warning.
-rw-r--r--src/tac.c5
1 files changed, 4 insertions, 1 deletions
diff --git a/src/tac.c b/src/tac.c
index 248afa9d7..777ec9193 100644
--- a/src/tac.c
+++ b/src/tac.c
@@ -506,7 +506,7 @@ copy_to_temp (FILE **g_tmp, char **g_tempfile, int input_fd, char const *file)
{
FILE *fp;
char *file_name;
- off_t bytes_copied = 0;
+ uintmax_t bytes_copied = 0;
if (!temp_stream (&fp, &file_name))
return -1;
@@ -527,6 +527,9 @@ copy_to_temp (FILE **g_tmp, char **g_tempfile, int input_fd, char const *file)
goto Fail;
}
+ /* Implicitly <= OFF_T_MAX due to preceding fwrite(),
+ but unsigned type used to avoid compiler warnings
+ not aware of this fact. */
bytes_copied += bytes_read;
}