From 352c7ed59422bb588eb8a6ab5ccb2b8f540a2d33 Mon Sep 17 00:00:00 2001
From: Lawrence Nahum <lawrence@greenaddress.it>
Date: Mon, 30 Mar 2020 11:21:24 +0200
Subject: [PATCH 1/2] honor CFLAGS, default to O2

---
 configure.ac | 8 ++------
 1 file changed, 2 insertions(+), 6 deletions(-)

diff --git a/configure.ac b/configure.ac
index ac0b70be8..c5750e209 100644
--- a/configure.ac
+++ b/configure.ac
@@ -10,10 +10,6 @@ AH_TOP([#ifndef LIBWALLYCORE_CONFIG_H
 AH_BOTTOM([#include "ccan_config.h"
 #endif /*LIBWALLYCORE_CONFIG_H*/])
 
-# Remove any optimisation/debug flags from CFLAGS, these are controlled
-# only by --enable-debug, in order to only use tested configurations
-CFLAGS=`echo $CFLAGS | sed 's/-[Og][0-9]*[ $$]*//'`
-
 LDPATH_VAR=LD_LIBRARY_PATH
 case $host_os in
 *darwin*)
@@ -144,14 +140,14 @@ if test "x$debug" == "xyes"; then
     fi
 else
     # Optimise and harden if we can
-    AX_CHECK_COMPILE_FLAG([-O3], [AM_CFLAGS="$AM_CFLAGS -O3"])
+    AX_CHECK_COMPILE_FLAG([-O2], [AM_CFLAGS="-O2 $AM_CFLAGS"])
     AC_CHECK_DEFINE([_FORTIFY_SOURCE], [], [
       AX_CHECK_COMPILE_FLAG([-D_FORTIFY_SOURCE=2],
         [CPPFLAGS="$CPPFLAGS -D_FORTIFY_SOURCE=2"])
     ])
     AX_CHECK_COMPILE_FLAG([-fstack-protector-strong], [AM_CFLAGS="$AM_CFLAGS -fstack-protector-strong"])
     AX_CHECK_COMPILE_FLAG([-DNDEBUG=1], [AM_CFLAGS="$AM_CFLAGS -DNDEBUG=1"])
-    AX_CHECK_LINK_FLAG([-O3], [LDFLAGS="$LDFLAGS -O3"])
+    AX_CHECK_LINK_FLAG([-O2], [LDFLAGS="-O2 $LDFLAGS"])
     AX_CHECK_LINK_FLAG([-Wl,-z,relro], [LDFLAGS="$LDFLAGS -Wl,-z,relro"])
 fi
 

From 1f4cc0cd0fb19849f0a1210420f23bd563919ef1 Mon Sep 17 00:00:00 2001
From: Lawrence Nahum <lawrence@greenaddress.it>
Date: Mon, 30 Mar 2020 12:03:29 +0200
Subject: [PATCH 2/2] patch secp256k1-zkp to use O2 rather than O3

---
 src/secp256k1/configure.ac | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/secp256k1/configure.ac b/src/secp256k1/configure.ac
index 6dfff78e0..ff384df2a 100644
--- a/src/secp256k1/configure.ac
+++ b/src/secp256k1/configure.ac
@@ -207,7 +207,7 @@ if test x"$enable_coverage" = x"yes"; then
     CFLAGS="$CFLAGS -O0 --coverage"
     LDFLAGS="$LDFLAGS --coverage"
 else
-    CFLAGS="$CFLAGS -O3"
+    CFLAGS="-O2 $CFLAGS"
 fi
 
 AC_MSG_CHECKING([for __builtin_popcount])