[gcc r12-5477] fixincludes: don't abort() on access failure [PR103306]

[gcc r12-5477] fixincludes: don't abort() on access failure [PR103306]

[Xi Ruoyao]

https://gcc.gnu.org/g:3363022ed810a2797c47867890547c8f73163257

commit r12-5477-g3363022ed810a2797c47867890547c8f73163257
Author: Xi Ruoyao <xry111@mengyan1223.wang>
Date:   Thu Nov 18 18:46:12 2021 +0800

    fixincludes: don't abort() on access failure [PR103306]
    
    Some distro may ship dangling symlinks in include directories, triggers
    the access failure.  Skip it and continue to next header instead of
    being to panic.
    
    Restore to old behavior before r12-5234 but without resurrecting the
    problematic getcwd() call, by using the environment variable "INPUT"
    exported by fixinc.sh.
    
    Tested on x86_64-linux-gnu, with a dangling symlink intentionally
    injected into /usr/include.
    
    fixincludes/
    
            PR bootstrap/103306
            * fixincl.c (process): Don't call abort().

Diff:
---
 fixincludes/fixincl.c | 15 ++++++++++++---
 1 file changed, 12 insertions(+), 3 deletions(-)

diff --git a/fixincludes/fixincl.c b/fixincludes/fixincl.c
index a17b65866c3..92909baf85f 100644
--- a/fixincludes/fixincl.c
+++ b/fixincludes/fixincl.c
@@ -1352,10 +1352,19 @@ process (void)
 
   if (access (pz_curr_file, R_OK) != 0)
     {
-      /* Some really strange error happened.  */
-      fprintf (stderr, "Cannot access %s: %s\n", pz_curr_file,
+      /* It may happens if for e. g. the distro ships some broken symlinks
+	 in /usr/include.  */
+
+      /* "INPUT" is exported in fixinc.sh, which is the pwd where fixincl
+	 runs.  It's used instead of getcwd to avoid allocating a buffer
+	 with unknown length.  */
+      const char *cwd = getenv ("INPUT");
+      if (!cwd)
+	cwd = "the working directory";
+
+      fprintf (stderr, "Cannot access %s from %s: %s\n", pz_curr_file, cwd,
 	       xstrerror (errno));
-      abort ();
+      return;
     }
 
   pz_curr_data = load_file (pz_curr_file);