# HG changeset patch
# User Tassilo Philipp
# Date 1495490906 -7200
# Node ID edbada931b3fa8a736248ae280c0e2aa2b07c416
# Parent  b625f2e11911499992c7f02b9e433cb4e9cf7015
configure:
- don't accidentally override set vars when checking for nonexecstack build flags
- comment cleanup

diff -r b625f2e11911 -r edbada931b3f configure
--- a/configure	Mon May 22 16:49:59 2017 +0200
+++ b/configure	Tue May 23 00:08:26 2017 +0200
@@ -203,14 +203,14 @@
 # Assure objects not asking for an execstack (or binary that links dyncall might end
 # up with one, for no reason).
 
-# We run our .s and .S files through $CC. GCC and others might (annoyingly) assume that
-# an executable stack may be required for those, if not told explicitly that it isn't.
-# Trying to specify this per source via .section .note.GNU-stack,"",... turned out to
-# be not consistently implemented across our supported platforms and toolchains, and
-# thus not being portable (on some platforms even resulting in the opposite, the mere
-# presence of this section, no matter the flags, creating an rwx stack).
-# So, let's set the needed build flags by running a few tests, if we find any that
-# work (as those also don't always have the intended effect).
+# .s.o/.S.o rules often use ${CC} which then invokes the tools needed. GCC and
+# others might (annoyingly) assume that an executable stack may be required for
+# those sources, if not told explicitly that it isn't.
+# Neither specifying this per source (e.g. via .section .note.GNU-stack,"",...), nor
+# per toolchain flags (e.g. as' --noexecstack) turned out to be portable across our
+# supported platforms, toolchains, and different versions of the latter (some even
+# producing the opposite result).
+# Find needed build flags by running a few tests; use default if none result in "rw-".
 
 RWXTESTPREFIX="rwxtest" # @@@ put this maybe all in Makefile.generic? out of source builds?
 for s in S s ; do (
@@ -218,10 +218,10 @@
   # asm test file, with main and _main for portability.
   (echo '.text';(echo '.globl main';echo 'main:') | sed 'p;s/m/_m/') > $RWXTESTPREFIX.$s
 
-  # Check var to be used, which depends on inference rules of this platform. E.g. ASFLAGS is only common
-  # on GNU, and on some other platforms only CFLAGS is used, ...
-  for f in "ASFLAGS=-Wa,--noexecstack" "ACFLAGS=-Wa,--noexecstack" "AFLAGS=--noexecstack" "CFLAGS+=-Wa,--noexecstack"; do
-    # Build a dummy makefile that triggers inference rules that dyncall's build also uses
+  # Check var to be used, which depends on inference rules of this platform. E.g. ASFLAGS is only common on GNU, and
+  # on some other platforms only CFLAGS is used, ... Check makes use of the config written so far, so use '+='.
+  for f in "ASFLAGS+=-Wa,--noexecstack" "ACFLAGS+=-Wa,--noexecstack" "AFLAGS+=--noexecstack" "CFLAGS+=-Wa,--noexecstack"; do
+    # dummy makefile triggering inference rules, reflecting dyncall's build
     make -f - <<MAKEFILE
 include $C
 $f
@@ -232,6 +232,7 @@
 
     # Check what stack of a built test binary would result in.
 # @@@ add xxd hexdump based versions for when objdump is not available; also check for those if we deal with ELF files
+# @@@ maybe also limit to ELF files
     STACKFLAGS=`(which objdump && objdump -p $RWXTESTPREFIX.out) | sed -e '/STACK/bx' -e 'd' -e ':x' -e 'N' -e 's/^.*flags[ \t]\([^ \t]*\).*/\1/'`
     rm $RWXTESTPREFIX.out $RWXTESTPREFIX.o
     if [ "$STACKFLAGS" = "rw-" ]; then