diff -Nru bglibs-2.04+dfsg/debian/changelog bglibs-2.04+dfsg/debian/changelog
--- bglibs-2.04+dfsg/debian/changelog	2025-10-04 18:45:36.000000000 +0200
+++ bglibs-2.04+dfsg/debian/changelog	2026-10-09 09:15:34.000000000 +0200
@@ -1,3 +1,9 @@
+bglibs (2.04+dfsg-10) UNRELEASED; urgency=medium
+
+  * d/p/msg-show-pid-lto.patch: prevent LTO from folding msg_show_pid
+
+ -- Sebastien Bacher <seb128@ubuntu.com>  Fri, 09 Oct 2026 07:15:34 +0000
+
 bglibs (2.04+dfsg-9) unstable; urgency=medium
 
   * QA upload.
diff -Nru bglibs-2.04+dfsg/debian/patches/msg-show-pid-lto.patch bglibs-2.04+dfsg/debian/patches/msg-show-pid-lto.patch
--- bglibs-2.04+dfsg/debian/patches/msg-show-pid-lto.patch	1970-01-01 01:00:00.000000000 +0100
+++ bglibs-2.04+dfsg/debian/patches/msg-show-pid-lto.patch	2026-10-09 09:15:34.000000000 +0200
@@ -0,0 +1,60 @@
+Description: msg: do not let LTO constant-fold the default msg_show_pid
+ libbg ships a default "const int msg_show_pid = 0" (msg/show_pid.c) which
+ programs are expected to override with their own definition (the header
+ declares it weak). When the library is built with -flto, GCC sees the
+ library-local const definition while linking libbg.so, folds the value to 0
+ and drops the whole PID-printing branch from msg_common()/msg_commonfv().
+ Programs such as mailfront that set msg_show_pid = 1 then silently lose the
+ "[pid]" in their log lines (and mailfront FTBFS because its testsuite
+ checks for it).
+ .
+ Marking the default definition weak is not sufficient (GCC still folds the
+ const initializer), so read the variable through a volatile lvalue instead.
+Author: Sebastien Bacher <seb128@ubuntu.com>
+Bug-Ubuntu: https://bugs.launchpad.net/bugs/2170282
+Forwarded: no
+Last-Update: 2026-10-09
+---
+This patch header follows DEP-3: http://dep.debian.net/deps/dep3/
+Index: bglibs-2.04+dfsg/msg/common.c
+===================================================================
+--- bglibs-2.04+dfsg.orig/msg/common.c
++++ bglibs-2.04+dfsg/msg/common.c
+@@ -17,8 +17,14 @@ void msg_common(const char* type,
+     msg_show_program = getenv("MSG_NO_PROGRAM") == NULL;
+   if (msg_show_program) {
+     obuf_puts(&errbuf, program);
+-    if (&msg_show_pid != 0 && msg_show_pid) {
+-      if (!pid || msg_show_pid < 0)
++    /* Read msg_show_pid through a volatile lvalue: the library carries a
++     * default definition (msg/show_pid.c) that programs override, and with
++     * LTO the compiler would otherwise constant-fold that default (0) and
++     * ignore the program's definition. */
++    const int show_pid = (&msg_show_pid != 0)
++      ? *(const volatile int*)&msg_show_pid : 0;
++    if (show_pid) {
++      if (!pid || show_pid < 0)
+ 	pid = getpid();
+       obuf_putc(&errbuf, '[');
+       obuf_putu(&errbuf, pid);
+Index: bglibs-2.04+dfsg/msg/commonf.c
+===================================================================
+--- bglibs-2.04+dfsg.orig/msg/commonf.c
++++ bglibs-2.04+dfsg/msg/commonf.c
+@@ -14,8 +14,14 @@ void msg_commonfv(const char* type,
+ {
+   if (program != 0) {
+     obuf_puts(&errbuf, program);
+-    if (&msg_show_pid != 0 && msg_show_pid) {
+-      if (!pid || msg_show_pid < 0)
++    /* Read msg_show_pid through a volatile lvalue: the library carries a
++     * default definition (msg/show_pid.c) that programs override, and with
++     * LTO the compiler would otherwise constant-fold that default (0) and
++     * ignore the program's definition. */
++    const int show_pid = (&msg_show_pid != 0)
++      ? *(const volatile int*)&msg_show_pid : 0;
++    if (show_pid) {
++      if (!pid || show_pid < 0)
+ 	pid = getpid();
+       obuf_putc(&errbuf, '[');
+       obuf_putu(&errbuf, pid);
diff -Nru bglibs-2.04+dfsg/debian/patches/series bglibs-2.04+dfsg/debian/patches/series
--- bglibs-2.04+dfsg/debian/patches/series	2025-10-04 18:45:36.000000000 +0200
+++ bglibs-2.04+dfsg/debian/patches/series	2026-10-09 09:15:34.000000000 +0200
@@ -1,3 +1,4 @@
 001_ensure_use_of_usr_bin_perl.patch
 declarations.patch
 0001-Fixes-for-new-GCC.patch
+msg-show-pid-lto.patch