POSIX says:
On some implementations, if buf is a null pointer, getcwd() may obtain
size bytes of memory using malloc(). In this case, the pointer returned
by getcwd() may be used as the argument in a subsequent call to free().
Invoking getcwd() with buf as a null pointer is not recommended in
conforming applications.
This produces an error building GCC with --enable-werror-always:
../../../fixincludes/fixincl.c: In function ‘process’:
../../../fixincludes/fixincl.c:1356:7: error: argument 1 is null but
the corresponding size argument 2 value is 4096 [-Werror=nonnull]
It's suggested by POSIX to call getcwd() with progressively larger
buffers until it does not give an [ERANGE] error. However, it's highly
unlikely that this error-handling route is ever used.
So we can simplify it instead of writting too much code. We give up to
use getcwd(), because `make` will output a `Leaving directory ...` message
containing the path to cwd when we call abort().
fixincludes/ChangeLog:
PR other/21823
PR bootstrap/80047
* fixincl.c (process): Simplify the handling for highly
unlikely access() failure, to avoid using non-standard
extensions.
---
fixincludes/fixincl.c | 9 ++++-----
1 file changed, 4 insertions(+), 5 deletions(-)
diff --git a/fixincludes/fixincl.c b/fixincludes/fixincl.c
index 6dba2f6e830..ee57fbf61b4 100644
--- a/fixincludes/fixincl.c
+++ b/fixincludes/fixincl.c
@@ -1352,11 +1352,10 @@ process (void)
if (access (pz_curr_file, R_OK) != 0)
{
- int erno = errno;
- fprintf (stderr, "Cannot access %s from %s\n\terror %d (%s)\n",
- pz_curr_file, getcwd ((char *) NULL, MAXPATHLEN),
- erno, xstrerror (erno));
- return;
+ /* Some really strange error happened. */
+ fprintf (stderr, "Cannot access %s: %s\n", pz_curr_file,
+ xstrerror (errno));
+ abort();
}
pz_curr_data = load_file (pz_curr_file);
--
2.33.1
> On Fri, 2021-11-12 at 12:59 -0800, Bruce Korb wrote:
> > If you are going to be excruciatingly, painfully correct, free() is
> > going to be unhappy about freeing a static string in the event
> > getcwd() fails for some inexplicable reason. I'd replace the free()
> +
> > return with a call to exit. Maybe even:
>
> It's free (buf), not free (cwd). buf won't point to a static string.
>
> buf may be NULL though, but free (NULL) is legal (no-op).
>
>
> > > if (VERY_UNLIKELY (access (pz_curr_file, R_OK) != 0)) abort()
>
> Perhaps just
>
> if (access (pz_curr_file, R_OK) != 0))
> {
> /* Some really inexplicable error happens. */
> fprintf (stderr, "Cannot access %s: %s",
> pz_curr_file, xstrerror (errno));
> abort();
> }
>
> It will show which file can't be accessed so it's possible to
> diagnose.
> And the working directory will be outputed by "make" when the fixincl
> command fails anyway, so we don't need to really care it.
