[Bug gcov-profile/101773] New: errors when writing to .gcda file are not checked

[Bug gcov-profile/101773] New: errors when writing to .gcda file are not checked

[vincent-gcc at vinc17 dot net]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=101773

            Bug ID: 101773
           Summary: errors when writing to .gcda file are not checked
           Product: gcc
           Version: 12.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: gcov-profile
          Assignee: unassigned at gcc dot gnu.org
          Reporter: vincent-gcc at vinc17 dot net
                CC: marxin at gcc dot gnu.org
  Target Milestone: ---

When I run a program compiled with -fprofile-generate, this program creates a
.gcda file, but write/close errors are not checked. With GCC 12.0.0 20210729
built from master and an almost full file system for the .gcda file:

$ gcc-test -O -fprofile-generate=dir tst.c
$ strace ./a.out
[...]
openat(AT_FDCWD, "dir/#home#vlefevre#a-tst.gcda", O_RDWR|O_CREAT, 0666) = 3
fcntl(3, F_SETLKW, {l_type=F_WRLCK, l_whence=SEEK_SET, l_start=0, l_len=0}) = 0
fcntl(3, F_GETFL)                       = 0x8002 (flags O_RDWR|O_LARGEFILE)
fstat(3, {st_mode=S_IFREG|0644, st_size=0, ...}) = 0
read(3, "", 1024)                       = 0
lseek(3, 0, SEEK_SET)                   = 0
write(3, "adcg 02B\21\20\217\20\0\0\0\241\10\0\0\0\1\0\0\0\1\0\0\0\0\0\0\1"...,
84) = -1 ENOSPC (No space left on device)
close(3)                                = 0
exit_group(0)                           = ?
+++ exited with 0 +++

Note that with gcc (Debian 10.2.1-6) 10.2.1 20210110, I get an error message:

$ ./a.out
libgcov profiling error:dir/#home#vlefevre#tst.gcda:Error writing

but the exit status is also 0, so that the error cannot be detected in scripts.

[Bug gcov-profile/101773] errors when writing to .gcda file are not checked

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=101773

--- Comment #1 from Richard Biener <rguenth at gcc dot gnu.org> ---
The question is what to do, exit() or alternatively simply stop attempting to
write to the file?  (or even remove it)

[Bug gcov-profile/101773] errors when writing to .gcda file are not checked

[vincent-gcc at vinc17 dot net]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=101773

--- Comment #2 from Vincent Lefèvre <vincent-gcc at vinc17 dot net> ---
An immediate exit() might yield other files, the terminal, etc. in a bad state.
IMHO, the best thing to do is to stop attempting to write to the file (possibly
attempt to remove it, but this might fail), and at the end, exit() with a
nonzero exit status.

[Bug gcov-profile/101773] errors when writing to .gcda file are not checked

[marxin at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=101773

Martin Liška <marxin at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
     Ever confirmed|0                           |1
   Last reconfirmed|                            |2021-08-04
             Status|UNCONFIRMED                 |NEW

--- Comment #3 from Martin Liška <marxin at gcc dot gnu.org> ---
Note we have a env variable that can achieve an immediate exit
(GCOV_EXIT_AT_ERROR):
https://gcc.gnu.org/onlinedocs/gcc-11.2.0/gcc/Gcov-and-Optimization.html

in that case, 1 is the exit code.

[Bug gcov-profile/101773] errors when writing to .gcda file are not checked

[vincent-gcc at vinc17 dot net]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=101773

--- Comment #4 from Vincent Lefèvre <vincent-gcc at vinc17 dot net> ---
GCOV_EXIT_AT_ERROR is not documented in the man page.

Anyway, it doesn't seem to work:

$ export GCOV_EXIT_AT_ERROR=1
$ printenv GCOV_EXIT_AT_ERROR
1
$ gcc-test -O -fprofile-generate=dir tst.c
$ ./a.out
$ echo $?
0
$ ls -l dir/*.gcda
-rw-r--r-- 1 vlefevre vlefevre 0 2021-08-04 14:48:01
dir/#home#vlefevre#a-tst.gcda

[Bug gcov-profile/101773] errors when writing to .gcda file are not checked

[marxin at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=101773

Martin Liška <marxin at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |WAITING

--- Comment #5 from Martin Liška <marxin at gcc dot gnu.org> ---
(In reply to Vincent Lefèvre from comment #4)
> GCOV_EXIT_AT_ERROR is not documented in the man page.

But we document that in GCC user manual.

> 
> Anyway, it doesn't seem to work:
> 
> $ export GCOV_EXIT_AT_ERROR=1
> $ printenv GCOV_EXIT_AT_ERROR
> 1
> $ gcc-test -O -fprofile-generate=dir tst.c
> $ ./a.out
> $ echo $?
> 0
> $ ls -l dir/*.gcda
> -rw-r--r-- 1 vlefevre vlefevre 0 2021-08-04 14:48:01
> dir/#home#vlefevre#a-tst.gcda

It works for me:

$ gcc --version
gcc (GCC) 12.0.0 20210804 (experimental)

$ df -h /tmp/ramdisk
Filesystem      Size  Used Avail Use% Mounted on
tmpfs           4.0K  4.0K     0 100% /tmp/ramdisk

$ g++ ~/Programming/tramp3d/tramp3d-v4.ii -fprofile-generate=/tmp/ramdisk
$ GCOV_EXIT_AT_ERROR=1 ./a.out -n 0
...
libgcov profiling
error:/tmp/ramdisk/#home#marxin#Programming#testcases#a-tramp3d-v4.gcda:Error
writing
profiling:exiting after an error
$ echo $?
1

$ ./a.out -n 0
...
libgcov profiling
error:/tmp/ramdisk/#home#marxin#Programming#testcases#a-tramp3d-v4.gcda:Error
writing
echo $?
0

[Bug gcov-profile/101773] errors when writing to .gcda file are not checked

[vincent-gcc at vinc17 dot net]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=101773

--- Comment #6 from Vincent Lefèvre <vincent-gcc at vinc17 dot net> ---
Created attachment 51259
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=51259&action=edit
added missing error check on fclose in gcc/gcov-io.c

Well, not all errors are detected. There is a missing test in gcc/gcov-io.c for
fclose (which does a write system call to flush the buffers):

--- a/gcc/gcov-io.c
+++ b/gcc/gcov-io.c
@@ -199,7 +199,8 @@ gcov_close (void)
 {
   if (gcov_var.file)
     {
-      fclose (gcov_var.file);
+      if (fclose (gcov_var.file))
+       gcov_var.error = 1;
       gcov_var.file = 0;
     }
   gcov_var.mode = 0;

(also in attachment). I've tested this patch, and it solves my problem:

openat(AT_FDCWD, "dir/#home#vlefevre#a-tst.gcda", O_RDWR|O_CREAT, 0666) = 3
fcntl(3, F_SETLKW, {l_type=F_WRLCK, l_whence=SEEK_SET, l_start=0, l_len=0}) = 0
fcntl(3, F_GETFL)                       = 0x8002 (flags O_RDWR|O_LARGEFILE)
fstat(3, {st_mode=S_IFREG|0644, st_size=0, ...}) = 0
read(3, "", 1024)                       = 0
lseek(3, 0, SEEK_SET)                   = 0
write(3, "adcg
02B\233\10\222\21\0\0\0\241\10\0\0\0\1\0\0\0\1\0\0\0\0\0\0\1"..., 84) = -1
ENOSPC (No space left on device)
close(3)                                = 0
write(2, "libgcov profiling error:dir/#hom"..., 68libgcov profiling
error:dir/#home#vlefevre#a-tst.gcda:Error writing
) = 68
write(2, "profiling:exiting after an error"..., 33profiling:exiting after an
error
) = 33
exit_group(1)                           = ?
+++ exited with 1 +++

[Bug gcov-profile/101773] errors when writing to .gcda file are not checked

[marxin at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=101773

Martin Liška <marxin at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|WAITING                     |NEW

--- Comment #7 from Martin Liška <marxin at gcc dot gnu.org> ---
(In reply to Vincent Lefèvre from comment #6)
> Created attachment 51259 [details]
> added missing error check on fclose in gcc/gcov-io.c
> 
> Well, not all errors are detected. There is a missing test in gcc/gcov-io.c
> for fclose (which does a write system call to flush the buffers):
> 
> --- a/gcc/gcov-io.c
> +++ b/gcc/gcov-io.c
> @@ -199,7 +199,8 @@ gcov_close (void)
>  {
>    if (gcov_var.file)
>      {
> -      fclose (gcov_var.file);
> +      if (fclose (gcov_var.file))
> +       gcov_var.error = 1;
>        gcov_var.file = 0;
>      }
>    gcov_var.mode = 0;
> 
> (also in attachment). I've tested this patch, and it solves my problem:

Great job! I was aware of the fclose, but didn't realize it fails during
flushing.
May I please install the patch on your behalf?

[Bug gcov-profile/101773] errors when writing to .gcda file are not checked

[vincent-gcc at vinc17 dot net]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=101773

--- Comment #8 from Vincent Lefèvre <vincent-gcc at vinc17 dot net> ---
(In reply to Martin Liška from comment #7)
> May I please install the patch on your behalf?

Yes. Thanks.

[Bug gcov-profile/101773] errors when writing to .gcda file are not checked

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=101773

--- Comment #9 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The master branch has been updated by Martin Liska <marxin@gcc.gnu.org>:

https://gcc.gnu.org/g:929f2cf4105ccf12d0684c6d5838f58f0ee5e7c7

commit r12-2736-g929f2cf4105ccf12d0684c6d5838f58f0ee5e7c7
Author: Vincent Lefèvre <vincent-gcc@vinc17.net>
Date:   Wed Aug 4 17:25:52 2021 +0200

    gcov: check return code of a fclose

    gcc/ChangeLog:

            PR gcov-profile/101773
            * gcov-io.c (gcov_close): Check return code of a fclose.

[Bug gcov-profile/101773] errors when writing to .gcda file are not checked

[marxin at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=101773

Martin Liška <marxin at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |RESOLVED
         Resolution|---                         |FIXED

--- Comment #10 from Martin Liška <marxin at gcc dot gnu.org> ---
Thanks for your cooperation, fixed on master.