sys-libs/glibc: restore strip quirk for 'libpthread.so.0'

This change effectively reverts commit e14229b10b513a
("sys-libs/glibc: drop prepallstrip, bug #587296")

gdb still relies on libpthread being unstripped.
See https://bugs.gentoo.org/697910 for details and reproducer.

Also see ebuild note that explains indirect mechanics
of how glibc relies on gdb's ability to traverse local symbols.

In EAPI=7 ebuilds (glibc-9999) we do selective stripping.

Reported-by: Minux
Closes: https://bugs.gentoo.org/697910
Bug: https://bugs.gentoo.org/587296
Bug: https://bugs.gentoo.org/46186
Signed-off-by: Sergei Trofimovich <slyfox@gentoo.org>
Package-Manager: Portage-2.3.76, Repoman-2.3.17
Signed-off-by: Sergei Trofimovich <slyfox@gentoo.org>

1 files changed, 22 insertions, 3 deletions

diff --git a/sys-libs/glibc/glibc-2.25-r11.ebuild b/sys-libs/glibc/glibc-2.25-r11.ebuild
index 4b3ac83a890b..0f544aa3101c 100644
--- a/sys-libs/glibc/glibc-2.25-r11.ebuild
+++ b/sys-libs/glibc/glibc-2.25-r11.ebuild
@@ -51,12 +51,31 @@ export CTARGET=${CTARGET:-${CHOST}}
 if [[ ${CTARGET} == ${CHOST} ]] ; then
 	if [[ ${CATEGORY} == cross-* ]] ; then
 		export CTARGET=${CATEGORY#cross-}
-		# portage's attempt to strip breaks non-native bianries
-		# at least on arm: bug #697428
-		RESTRICT=strip
 	fi
 fi
 
+# Note [Disable automatic stripping]
+# Disabling automatic stripping for a few reasons:
+# - portage's attempt to strip breaks non-native binaries at least on
+#   arm: bug #697428
+# - portage's attempt to strip libpthread.so.0 breaks gdb thread
+#   enumeration: bug #697910. This is quite subtle:
+#   * gdb uses glibc's libthread_db-1.0.so to enumerate threads.
+#   * libthread_db-1.0.so needs access to libpthread.so.0 local symbols
+#     via 'ps_pglobal_lookup' symbol defined in gdb.
+#   * 'ps_pglobal_lookup' uses '.symtab' section table to resolve all
+#     known symbols in 'libpthread.so.0'. Specifically 'nptl_version'
+#     (unexported) is used to sanity check compatibility before enabling
+#     debugging.
+#     Also see https://sourceware.org/gdb/wiki/FAQ#GDB_does_not_see_any_threads_besides_the_one_in_which_crash_occurred.3B_or_SIGTRAP_kills_my_program_when_I_set_a_breakpoint
+#   * normal 'strip' command trims '.symtab'
+#   Thus our main goal here is to prevent 'libpthread.so.0' from
+#   losing it's '.symtab' entries.
+# As Gentoo's strip does not allow us to pass less aggressive stripping
+# options and does not check the machine target we disable stripping
+# entirely.
+RESTRICT=strip
+
 is_crosscompile() {
 	[[ ${CHOST} != ${CTARGET} ]]
 }