Fix a long-standing bug where Clang had a different default from GCC on

Linux and other (non-Darwin) platforms and have it use -fmath-errno by
default (for better or worse).

Darwin has seen the light here and uses -fno-math-errno by default, this
patch preserves that.

If any maintainers for a non-Linux platform would also like to opt-in to
-fno-math-errno by default, I'm happy to add folks, but we're currently
getting buts and misleading comparisons with GCC due to this difference
in behavior on Linux at least.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@155607 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 7 insertions, 8 deletions

diff --git a/lib/Driver/Tools.cpp b/lib/Driver/Tools.cpp
index b61b8dcf2d..13d9820159 100644
--- a/lib/Driver/Tools.cpp
+++ b/lib/Driver/Tools.cpp
@@ -1617,16 +1617,15 @@ void Clang::ConstructJob(Compilation &C, const JobAction &JA,
         A->getOption().getID() != options::OPT_fhonor_nans)
       CmdArgs.push_back("-menable-no-nans");
 
-  // -fno-math-errno is default.
-  bool MathErrno = false;
+  // -fno-math-errno is default on Darwin. Other platforms, -fmath-errno is the
+  // default.
+  bool MathErrno = !getToolChain().getTriple().isOSDarwin();
   if (Arg *A = Args.getLastArg(options::OPT_ffast_math,
                                options::OPT_fmath_errno,
-                               options::OPT_fno_math_errno)) {
-    if (A->getOption().getID() == options::OPT_fmath_errno) {
-      CmdArgs.push_back("-fmath-errno");
-      MathErrno = true;
-    }
-  }
+                               options::OPT_fno_math_errno))
+    MathErrno = A->getOption().getID() == options::OPT_fmath_errno;
+  if (MathErrno)
+    CmdArgs.push_back("-fmath-errno");
 
   // There are several flags which require disabling very specific
   // optimizations. Any of these being disabled forces us to turn off the