Avoid running $(CXX) during build to obtain header file paths

This reduces the build time somewhat and is particularly noticeable
during rebuilds with few code changes.

1 files changed, 14 insertions, 0 deletions

diff --git a/configure b/configure
index 17625e1..6ff2527 100755
--- a/configure
+++ b/configure
@@ -635,6 +635,8 @@ BISON
 INSTALL_INFO
 PERL
 BASH_SHELL
+CXX_CMATH_HEADER
+CXX_CSTDLIB_HEADER
 CXX_SYSINCLUDES
 SYSINCLUDES
 AUTOCONF
@@ -5054,6 +5056,18 @@ fi
 
 
 
+# Obtain some C++ header file paths.  This is used to make a local
+# copy of those headers in Makerules.
+if test -n "$CXX"; then
+  find_cxx_header () {
+    echo "#include <$1>" | $CXX -M -MP -x c++ - | sed -n "/$1:/{s/:\$//;p}"
+  }
+  CXX_CSTDLIB_HEADER="$(find_cxx_header cstdlib)"
+  CXX_CMATH_HEADER="$(find_cxx_header cmath)"
+fi
+
+
+
 # Test if LD_LIBRARY_PATH contains the notation for the current directory
 # since this would lead to problems installing/building glibc.
 # LD_LIBRARY_PATH contains the current directory if one of the following