On 10/08/2014 02:12 AM, Jim Meyering wrote: > On Tue, Oct 7, 2014 at 5:36 PM, Pádraig Brady <[email protected]> wrote: >> On 10/08/2014 12:51 AM, Paul Eggert wrote: >>> Paul Eggert wrote: >>> >>>> The attached patch still needs a changelog entry and test cases. >>> >>> I wrote those up and pushed the attached patch; this should fix the bug so >>> I'm closing the bug report. >> >> I was just going through the patch as it happens, and I found no issues. >> I see the tac changes should also avoid erroneous errors if a file was >> truncated while reading for example. >> I pushed a follow up to avoid some new syntax check errors. >> >> thanks! >> Pádraig. > > I pushed a patch to avoid a new failiure of the > split/b-chunk.sh test on non-Linux.
The attached is needed to avoid a new warning on 32 bit. thanks, Pádraig.
>From 16c7267d7425fe59b6919e77fa572d104d72c2bf Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?P=C3=A1draig=20Brady?= <[email protected]> Date: Wed, 8 Oct 2014 12:35:36 +0100 Subject: [PATCH] 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. --- src/tac.c | 5 ++++- 1 files changed, 4 insertions(+), 1 deletions(-) diff --git a/src/tac.c b/src/tac.c index 248afa9..777ec91 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; } -- 1.7.7.6
