From 613c34cd869e56dee2ea5fb701f05b07da7069c8 Mon Sep 17 00:00:00 2001
From: Jonas Nick <jonasd.nick@gmail.com>
Date: Tue, 17 Dec 2019 12:34:26 +0000
Subject: [PATCH 1/4] Remove test in configure.ac because it doesn't have an
 effect

---
 configure.ac | 4 ----
 1 file changed, 4 deletions(-)

diff --git a/configure.ac b/configure.ac
index 2a8db0a51c607..0a94f15501873 100644
--- a/configure.ac
+++ b/configure.ac
@@ -19,10 +19,6 @@ AC_PATH_TOOL(RANLIB, ranlib)
 AC_PATH_TOOL(STRIP, strip)
 AX_PROG_CC_FOR_BUILD
 
-if test "x$CFLAGS" = "x"; then
-  CFLAGS="-g"
-fi
-
 AM_PROG_CC_C_O
 
 AC_PROG_CC_C89

From ecba8138ec163f5ad4c303df9f8744810a3dfc03 Mon Sep 17 00:00:00 2001
From: Jonas Nick <jonasd.nick@gmail.com>
Date: Tue, 17 Dec 2019 12:37:48 +0000
Subject: [PATCH 2/4] Append instead of Prepend user-CFLAGS to default CFLAGS
 allowing the user to override default variables

---
 configure.ac | 14 +++++++-------
 1 file changed, 7 insertions(+), 7 deletions(-)

diff --git a/configure.ac b/configure.ac
index 0a94f15501873..424f6efb20f6b 100644
--- a/configure.ac
+++ b/configure.ac
@@ -59,11 +59,11 @@ case $host_os in
    ;;
 esac
 
-CFLAGS="$CFLAGS -W"
+CFLAGS="-W $CFLAGS"
 
 warn_CFLAGS="-std=c89 -pedantic -Wall -Wextra -Wcast-align -Wnested-externs -Wshadow -Wstrict-prototypes -Wno-unused-function -Wno-long-long -Wno-overlength-strings"
 saved_CFLAGS="$CFLAGS"
-CFLAGS="$CFLAGS $warn_CFLAGS"
+CFLAGS="$warn_CFLAGS $CFLAGS"
 AC_MSG_CHECKING([if ${CC} supports ${warn_CFLAGS}])
 AC_COMPILE_IFELSE([AC_LANG_SOURCE([[char foo;]])],
     [ AC_MSG_RESULT([yes]) ],
@@ -72,7 +72,7 @@ AC_COMPILE_IFELSE([AC_LANG_SOURCE([[char foo;]])],
     ])
 
 saved_CFLAGS="$CFLAGS"
-CFLAGS="$CFLAGS -fvisibility=hidden"
+CFLAGS="-fvisibility=hidden $CFLAGS"
 AC_MSG_CHECKING([if ${CC} supports -fvisibility=hidden])
 AC_COMPILE_IFELSE([AC_LANG_SOURCE([[char foo;]])],
     [ AC_MSG_RESULT([yes]) ],
@@ -173,10 +173,10 @@ AC_CHECK_TYPES([__int128])
 
 if test x"$enable_coverage" = x"yes"; then
     AC_DEFINE(COVERAGE, 1, [Define this symbol to compile out all VERIFY code])
-    CFLAGS="$CFLAGS -O0 --coverage"
-    LDFLAGS="$LDFLAGS --coverage"
+    CFLAGS="-O0 --coverage $CFLAGS"
+    LDFLAGS="--coverage $LDFLAGS"
 else
-    CFLAGS="$CFLAGS -O3"
+    CFLAGS="-O3 $CFLAGS"
 fi
 
 if test x"$use_ecmult_static_precomputation" != x"no"; then
@@ -194,7 +194,7 @@ if test x"$use_ecmult_static_precomputation" != x"no"; then
 
   warn_CFLAGS_FOR_BUILD="-Wall -Wextra -Wno-unused-function"
   saved_CFLAGS="$CFLAGS"
-  CFLAGS="$CFLAGS $warn_CFLAGS_FOR_BUILD"
+  CFLAGS="$warn_CFLAGS_FOR_BUILD $CFLAGS"
   AC_MSG_CHECKING([if native ${CC_FOR_BUILD} supports ${warn_CFLAGS_FOR_BUILD}])
   AC_COMPILE_IFELSE([AC_LANG_SOURCE([[char foo;]])],
       [ AC_MSG_RESULT([yes]) ],

From 83fb1bcef49b1c12ef349f62d90bfcc83f0f7398 Mon Sep 17 00:00:00 2001
From: Jonas Nick <jonasd.nick@gmail.com>
Date: Tue, 17 Dec 2019 12:41:44 +0000
Subject: [PATCH 3/4] Remove -O2 from default CFLAGS because this would
 override the -O3 flag (see AC_PROG_CC in the Autoconf manual)

---
 configure.ac | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/configure.ac b/configure.ac
index 424f6efb20f6b..a68ef9586951b 100644
--- a/configure.ac
+++ b/configure.ac
@@ -7,6 +7,10 @@ AH_TOP([#ifndef LIBSECP256K1_CONFIG_H])
 AH_TOP([#define LIBSECP256K1_CONFIG_H])
 AH_BOTTOM([#endif /*LIBSECP256K1_CONFIG_H*/])
 AM_INIT_AUTOMAKE([foreign subdir-objects])
+
+# Set -g (but not -O2 because this would override -O3 which we're adding later)
+# if CFLAGS are not already set (see PROG_CC in the Autoconf manual)
+: ${CFLAGS="-g"}
 LT_INIT
 
 dnl make the compilation flags quiet unless V=1 is used

From ca739cba238cdd7c513abfc719b0b0eb957c9458 Mon Sep 17 00:00:00 2001
From: Jonas Nick <jonasd.nick@gmail.com>
Date: Wed, 19 Feb 2020 14:07:54 +0000
Subject: [PATCH 4/4] Compile with optimization flag -O2 by default instead of
 -O3

---
 configure.ac | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/configure.ac b/configure.ac
index a68ef9586951b..1272262ad4261 100644
--- a/configure.ac
+++ b/configure.ac
@@ -8,8 +8,9 @@ AH_TOP([#define LIBSECP256K1_CONFIG_H])
 AH_BOTTOM([#endif /*LIBSECP256K1_CONFIG_H*/])
 AM_INIT_AUTOMAKE([foreign subdir-objects])
 
-# Set -g (but not -O2 because this would override -O3 which we're adding later)
-# if CFLAGS are not already set (see PROG_CC in the Autoconf manual)
+# Set -g if CFLAGS are not already set, which matches the default autoconf
+# behavior (see PROG_CC in the Autoconf manual) with the exception that we don't
+# set -O2 here because we set it in any case (see further down).
 : ${CFLAGS="-g"}
 LT_INIT
 
@@ -180,7 +181,7 @@ if test x"$enable_coverage" = x"yes"; then
     CFLAGS="-O0 --coverage $CFLAGS"
     LDFLAGS="--coverage $LDFLAGS"
 else
-    CFLAGS="-O3 $CFLAGS"
+    CFLAGS="-O2 $CFLAGS"
 fi
 
 if test x"$use_ecmult_static_precomputation" != x"no"; then