From afce89dac1a3cdb975da72020acdba16940fd679 Mon Sep 17 00:00:00 2001
From: Pau Espin Pedrol <pespin@sysmocom.de>
Date: Tue, 6 Aug 2019 12:46:46 +0200
Subject: configure: Allow disabling workaround for TLS bug in old ARM gcc
 versions

Some toolchains (such as sysmobts 201705 one) containing the TLS bug on
old ARM gcc versions (<7.3.0) also crash if the initial workaround found
is aplied (CFLAGS="-mtls-dialect=gnu2"). In that scenario, let's provide
a way to disable the workaround (to avoid "ld" crashing) and warn the
user about requirement to build with -O0 to avoid runtime crashes.

Related: OS#4062
Related: SYS#4628
Change-Id: I04ff8c702eabcf4f6e7b59e11aece2744267cefe
---
 configure.ac                |  3 +--
 m4/check_tls_gcc_arm_bug.m4 | 22 ++++++++++++++++++++++
 2 files changed, 23 insertions(+), 2 deletions(-)

diff --git a/configure.ac b/configure.ac
index 3764e29e..7ad5908d 100644
--- a/configure.ac
+++ b/configure.ac
@@ -123,8 +123,7 @@ AC_DEFUN([CHECK_TM_INCLUDES_TM_GMTOFF], [
 CHECK_TM_INCLUDES_TM_GMTOFF
 
 dnl Check if We need to apply workaround for TLS bug on ARM platform for GCC < 7.3.0:
-CHECK_TLS_GCC_ARM_BUG
-CFLAGS="$CFLAGS $TLS_GCC_ARM_BUG_CFLAGS"
+ARG_ENABLE_DETECT_TLS_GCC_ARM_BUG
 
 dnl Generate the output
 AC_CONFIG_HEADER(config.h)
diff --git a/m4/check_tls_gcc_arm_bug.m4 b/m4/check_tls_gcc_arm_bug.m4
index 73b3e957..cee20e65 100644
--- a/m4/check_tls_gcc_arm_bug.m4
+++ b/m4/check_tls_gcc_arm_bug.m4
@@ -27,3 +27,25 @@ AC_DEFUN([CHECK_TLS_GCC_ARM_BUG], [
   AC_SUBST([TLS_GCC_ARM_BUG_CFLAGS])
   AC_MSG_RESULT([$TLS_GCC_ARM_BUG_CFLAGS])
 ])
+
+# Allow disabling the check in order to workaround bug by letting user pass
+# CFLAGS="-O0" on toolchains that crash when "-mtls-dialect=gnu2" is used.
+# CFLAGS is updated with workaround if detection is enabled and workaround is needed.
+AC_DEFUN([ARG_ENABLE_DETECT_TLS_GCC_ARM_BUG], [
+  AC_ARG_ENABLE(detect_tls_gcc_arm_bug,
+    [AS_HELP_STRING(
+      [--disable-detect-tls-gcc-arm-bug],
+      [Disable detecting and applying workaround for TLS bug on ARM platform for GCC < 7.3.0]
+    )],
+    [detect_tls_gcc_arm_bug=$enableval], [detect_tls_gcc_arm_bug="yes"])
+  if test x"$detect_tls_gcc_arm_bug" = x"yes"; then
+    CHECK_TLS_GCC_ARM_BUG
+    if test "x$TLS_GCC_ARM_BUG_CFLAGS" != "x"; then
+      CFLAGS="$CFLAGS $TLS_GCC_ARM_BUG_CFLAGS"
+      AC_MSG_WARN([Applying workaround for TLS bug on ARM platform for GCC < 7.3.0
+                  ($TLS_GCC_ARM_BUG_CFLAGS). On some toolchain versions, ld may
+                  crash. In that case you must build with CFLAGS='-O0' and run
+                  ./configure with --disable-detect-tls-gcc-arm-bug])
+    fi
+fi
+])
-- 
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