[Bug binutils/27284] New: ar: wrong permissions on output file

[ats-sourceware at offog dot org]

https://sourceware.org/bugzilla/show_bug.cgi?id=27284

            Bug ID: 27284
           Summary: ar: wrong permissions on output file
           Product: binutils
           Version: 2.36
            Status: UNCONFIRMED
          Severity: normal
          Priority: P2
         Component: binutils
          Assignee: unassigned at sourceware dot org
          Reporter: ats-sourceware at offog dot org
  Target Milestone: ---

I've just run into an interesting problem when building plan9port with
binutils 2.36: it uses "ar rcs" to build static libraries, but one of
the libraries -- lib9.a, which has a very long list of objects -- ends
up with permission 0600 rather than the intended 0644.

Here's a script that reproduces the problem for me on amd64 GNU/Linux
with GCC 10.2.0:

-----
#!/bin/sh

echo "int x;" >t.c
gcc -c t.c
for i in $(seq 100 299); do
        cp t.o $i.o
done

rm -f libt.a
ar rcs libt.a 1*.o
ls -l libt.a

rm -f libt.a
ar rcs libt.a [12]*.o
ls -l libt.a
-----

This produces the output:

-rw-r--r-- 1 root root 101072 Jan 29 22:23 libt.a
-rw------- 1 root root 202072 Jan 29 22:23 libt.a

Tracing through the ar code, this seems to be fallout from this change:
https://lists.gnu.org/archive/html/bug-binutils/2021-01/msg00089.html

In write_archive, with the shorter argument list, iarch->iostream is
non-NULL; with the longer list, iarch->iostream is NULL, and skip_stat
is set to TRUE, so the permissions don't get set.

It looks from the libbfd code like ->iostream can legitimately be NULL
while the file is open, so I think the new test in write_archive is
incorrect.

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