[PATCH] D38984: Use fopen instead of fdopen for opening GCDA files as fdopen seems to cause files to get corrupted

[Zachary Turner via llvm-commits]

Try passing _O_BINARY to the original open() call and then seeing if fdopen
works.

If you really want true reliability you should use native win32 APIs for
file i/o, but that’s a large rewrite, so I agree targeted fixes make more
sense here
On Mon, Oct 16, 2017 at 5:14 PM Marco Castelluccio via Phabricator <
reviews at reviews.llvm.org> wrote:

> marco-c created this revision.
>
> Fixes https://bugs.llvm.org/show_bug.cgi?id=34922.
>
> When using fdopen, the GCDA file is very often not correctly written to
> disk. I honestly have no idea why, perhaps somebody more familiar with
> Windows would know.
> This doesn't only apply to the simple case from bug 34922. I have built
> Firefox to collect coverage and before this change most GCDA files were
> corrupted.
>
>
> https://reviews.llvm.org/D38984
>
> Files:
>   lib/profile/GCDAProfiling.c
>
>
> Index: lib/profile/GCDAProfiling.c
> ===================================================================
> --- lib/profile/GCDAProfiling.c
> +++ lib/profile/GCDAProfiling.c
> @@ -263,8 +263,9 @@
>     * same GCDA. This can fail if the filesystem doesn't support it, but
> in that
>     * case we'll just carry on with the old racy behaviour and hope for
> the best.
>     */
> -  flock(fd, LOCK_EX);
> -  output_file = fdopen(fd, mode);
> +  close(fd);
> +  output_file = fopen(filename, mode);
> +  flock(fileno(output_file), LOCK_EX);
>
>    /* Initialize the write buffer. */
>    write_buffer = NULL;
> @@ -462,7 +463,7 @@
>        unmap_file();
>      }
>
> -    flock(fd, LOCK_UN);
> +    flock(fileno(output_file), LOCK_UN);
>      fclose(output_file);
>      output_file = NULL;
>      write_buffer = NULL;
>
>
>
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