From: Matthew Fernandez <matthew.fernandez@gmail.com>
Date: Wed, 12 Oct 2022 04:10:54 +0000 (-0700)
Subject: stop enabling -ffast-math on any platform
X-Git-Tag: 7.0.0~14^2~1
X-Git-Url: https://granicus.if.org/sourcecode?a=commitdiff_plain;h=404e8aa21385d50b268d739fe39927ba02327af8;p=graphviz

stop enabling -ffast-math on any platform

The `-ffast-math` compiler option enables a mode of floating point semantics
that are heavily relaxed from strict IEEE 754 conformance in the name of speed.¹
The permissible optimizations under `-ffast-math` include transformations that
produce floating point results most users would consider wrong. It is unclear
why “do math fast but incorrectly” is a useful mode. It seems the world is
finally coming around to this tenet.²

This change stops enabling `-ffast-math` anywhere in the Autotools build system.

Gitlab: fixes #1412, #2296
Reported-by: Kasper Daniel Hansen
Reported-by: Ross Barnowski

¹ https://gcc.gnu.org/wiki/FloatingPointMath
² https://simonbyrne.github.io/notes/fastmath/,
  https://moyix.blogspot.com/2022/09/someones-been-messing-with-my-subnormals.html
---

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 2a8265b46..c3cf7ddcb 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -18,6 +18,13 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
   no longer suppresses `-ffast-math`. Users relying on this are encouraged to
   investigate what in their build environment is appending a flag their C
   compiler does not support.
+- The `-ffast-math` compiler flag is no longer enabled by the Autotools build
+  system.
+
+### Fixed
+
+- Issues with GCC 8, `-O3` and `-ffast-math` #1412
+- Problem building Graphviz-5.0.1: undefined symbols `__*_finite` #2296
 
 ### Removed
 
diff --git a/configure.ac b/configure.ac
index 49dd28cef..33febee1a 100644
--- a/configure.ac
+++ b/configure.ac
@@ -396,10 +396,10 @@ else
 	        LDFLAGS="${LDFLAGS} -Wl,-headerpad_max_install_names"
 	        ;;
 	    *-freebsd* )
-	        CFLAGS="${CFLAGS} -Wstrict-prototypes -Wpointer-arith -Wall -ffast-math"
+	        CFLAGS="${CFLAGS} -Wstrict-prototypes -Wpointer-arith -Wall"
 		    ;;
 	    * )
-	        CFLAGS="${CFLAGS} -Wno-unknown-pragmas -Wstrict-prototypes -Wpointer-arith -Wall -ffast-math"
+	        CFLAGS="${CFLAGS} -Wno-unknown-pragmas -Wstrict-prototypes -Wpointer-arith -Wall"
 	        ;;
 	    esac
 	    ;;