gcc: disable annoying code quoting.

Newer versions of gcc add a lot of aggravating spewage to the
diagnostics, by including copies of the lines of code where
the error occurs followed by a line showing the error location
with a caret and some tilde underlining.

* configure: new test to see whether the compiler emits a
caret line for a program that has a syntax error (missing
closing brace). If so, we test whether the compiler accepts
the option -fno-diagnostics-show-caret, and if so, we add
that option to DIAG_FLAGS in config.make.

1 files changed, 27 insertions, 0 deletions

diff --git a/configure b/configure
index d157c5b2..a621a9f8 100755
--- a/configure
+++ b/configure
@@ -908,6 +908,33 @@ else
   printf " n/a\n"
 fi
 
+printf "Checking for disabling source code quoting in compiler errors ... "
+
+cat > conftest.c <<!
+#include <stdio.h>
+int main(void)
+{
+!
+
+if ! conftest && grep -q -E '^ +\^' conftest.err ; then
+  cat > conftest.c <<!
+#include <stdio.h>
+int main(void)
+{
+return 0;
+}
+!
+  opt=-fno-diagnostics-show-caret
+  if conftest EXTRA_FLAGS=$opt ; then
+    printf "needed\n"
+    diag_flags="$diag_flags $opt"
+  else
+    printf "unable\n"
+  fi
+else
+  printf "no need\n"
+fi
+
 #
 # Check for annoying clashes from non-conforming BSD-derived systems that don't
 # honor Unix/POSIX feature selection macros!