From 717e821b99797845e1bef47d862f8cb0fb69cfc9 Mon Sep 17 00:00:00 2001
From: Niklas Hambüchen <mail@nh2.me>
Date: Tue, 2 Jul 2019 22:30:15 +0200
Subject: autoconf: Allow overriding CFLAGS/CXXFLAGS from outside.

As is normal for autoconf-based projects.

For example, it is a common use case to do

    ./configure CXXFLAGS=-O0

This did not work for nix until now, because the `CXXFLAGS=` declaration
would unconditionally erase what the user had specified.

The custom `OPTIMIZE` flag is removed, but the default `-O3` is retained;
autoconf would default to `-g -O2` by default otherwise as documented on:

https://www.gnu.org/software/autoconf/manual/autoconf-2.60/html_node/C-Compiler.html
https://www.gnu.org/software/autoconf/manual/autoconf-2.60/html_node/C_002b_002b-Compiler.html
---
 configure.ac | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

(limited to 'configure.ac')

diff --git a/configure.ac b/configure.ac
index 3a486fab8e71..571bb54d8a18 100644
--- a/configure.ac
+++ b/configure.ac
@@ -50,8 +50,10 @@ AC_DEFINE_UNQUOTED(SYSTEM, ["$system"], [platform identifier ('cpu-os')])
 test "$localstatedir" = '${prefix}/var' && localstatedir=/nix/var
 
 
-CFLAGS=
-CXXFLAGS=
+# Set default flags for nix (as per AC_PROG_CC/CXX docs),
+# while still allowing the user to override them from the command line.
+: ${CFLAGS="-O3"}
+: ${CXXFLAGS="-O3"}
 AC_PROG_CC
 AC_PROG_CXX
 AC_PROG_CPP
-- 
cgit 1.4.1