[PATCH] Fix assert after goto failure

[Tom de Vries <tdevries@suse.de>]

Hi,

Consider the following code in function dwz:
...
      else if (write_aranges (dso))
       {
	 cleanup ();
       failure:
	 ret = 1;
       }
       ...
		      char *p1 = realpath (file, NULL);
		      char *p2 = realpath (multifile, NULL);
		      ...
		      if (p1 == NULL || p2 == NULL)
			{
			  ...
			  error (0, 0, "Could not compute relative multifile "
				       "pathname from %s to %s",
				 file, multifile);
			  goto failure;
...

I've managed to triggered this error in the following way.

First we do this setup:
...
$ mkdir tmpdir
$ ln -s tmpdir tmpdir-slink
$ cp hello 1
$ cp 1 2
...

Then we want to run dwz with a common file in tmpdir using the symlink tmpdir-slink:
...
$ dwz -m ./tmpdir-slink/3 -r 1 2
...
but, stop just before calling realpath and remove the symlink to make the p2
realpath call return NULL.

We can do that using gdb:
...
$ gdb -batch \
  -ex "b 15451" \
  -ex run \
  -ex "shell rm -f tmpdir-slink" \
  -ex cont \
  --args ./dwz -m ./tmpdir-slink/3 -r 1 2
Breakpoint 1 at 0x382d1: file dwz.c, line 15451.

Breakpoint 1, dwz (file=0x7fffffffe285 "1", outfile=0x0, res=0x5555557a5260,
                   resa=0x0, files=0x7fffffffdeb8) at dwz.c:15451
15451			  if (!multifile_relative)
dwz: Could not compute relative multifile pathname from 1 to ./tmpdir-slink/3
dwz: dwz.c:2170: off_htab_add_die: Assertion `*slot == NULL' failed.

Program received signal SIGABRT, Aborted.
0x00007ffff75fffb7 in raise () from /lib/x86_64-linux-gnu/libc.so.6
...
but we hit an assertion.

This is because cleanup is not called.

Fix this by moving the failure label up one line.

Any comments?

Thanks,
- Tom

Fix assert after goto failure

2021-03-01  Tom de Vries  <tdevries@suse.de>

	* dwz.c (dwz): Move failure label to before cleanup.

---
 dwz.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/dwz.c b/dwz.c
index 8eb4f1d..d5fe7b1 100644
--- a/dwz.c
+++ b/dwz.c
@@ -15434,8 +15434,8 @@ dwz (const char *file, const char *outfile, struct file_result *res,
 	}
       else if (write_aranges (dso))
 	{
-	  cleanup ();
 	failure:
+	  cleanup ();
 	  ret = 1;
 	}
       else