Description: shm_segments: use the PowerPC offset of shm_segsz on PowerPC
 PowerPC orders struct shmid_ds with the three time fields before shm_segsz;
 the generic layout puts shm_segsz first. The fixed offset therefore reads
 shm_atime on ppc64el and ppc64, and the oversized value makes the following
 shmread() fail, so the segment never reaches %segments. That fails
 t/72-shm_segments.t and t/74-seg_map.t.
 .
 Minimal alternative to portable-shmid_ds.patch; use one or the other.
Author: Edmund Lodewijks <edmund@proteamail.com>
Forwarded: https://github.com/stevieb9/ipc-shareable/issues/66
Last-Update: 2026-08-28
---
--- a/lib/IPC/Shareable.pm
+++ b/lib/IPC/Shareable.pm
@@ -723,10 +723,16 @@
         my $stat_buf = '';
         shmctl($id, IPC_STAT, $stat_buf) or next;
 
+        # PowerPC orders struct shmid_ds with the three time fields before
+        # shm_segsz; everywhere else shm_segsz comes first, right after
+        # ipc_perm. Both ipc_perm layouts are 48 bytes, so shm_segsz sits at
+        # 72 rather than 48 on 64-bit, and at 76 rather than 36 on 32-bit.
+        my $ppc = $Config{archname} =~ /^(?:powerpc|ppc)/i;
+
         my ($segsz) = $^O eq 'linux'
             ? ( $Config{longsize} == 8
-            ? unpack('x[48] Q', $stat_buf)   # 64-bit Linux
-            : unpack('x[36] L', $stat_buf) ) # 32-bit Linux
+            ? unpack($ppc ? 'x[72] Q' : 'x[48] Q', $stat_buf)   # 64-bit Linux
+            : unpack($ppc ? 'x[76] L' : 'x[36] L', $stat_buf) ) # 32-bit Linux
             : $^O eq 'freebsd' && $Config{longsize} == 8
             ? unpack('x[32] Q', $stat_buf)   # 64-bit FreeBSD (key_t=long=8, ipc_perm=32)
             : $^O eq 'solaris'