From: Jan Engelhardt <jengelh@inai.de>
Date: 2014-06-18 19:13:44.267333132 +0200

The project builds C++ files, but _CFLAGS only applies to .c files.
The flags must go into _CPPFLAGS for all languages' preprocessor.
---
 m4/ac_check_cxsc.m4 |   12 ++++++------
 src/Makefile.am     |    2 +-
 2 files changed, 7 insertions(+), 7 deletions(-)

Index: float-0.7.3/m4/ac_check_cxsc.m4
===================================================================
--- float-0.7.3.orig/m4/ac_check_cxsc.m4
+++ float-0.7.3/m4/ac_check_cxsc.m4
@@ -1,5 +1,5 @@
 # check for cxsc library
-# sets CXSC_CFLAGS, CXSC_LDFLAGS, CXSC_MAKELIB and CXSC_LIBS,
+# sets CXSC_CPPFLAGS, CXSC_LDFLAGS, CXSC_MAKELIB and CXSC_LIBS,
 # and CXSC_WITH, CXSC_DEPEND,
 # and CXSC=yes/no/extern
 
@@ -43,7 +43,7 @@ AC_ARG_WITH(cxsc,
   else
     CXSC_WITH="$CXSC_WITH --with-cxsc=$withval"
     CXSC=yes
-    CXSC_CFLAGS="-I$withval/include"; CXSC_LDFLAGS="-L$withval/lib"
+    CXSC_CPPFLAGS="-I$withval/include"; CXSC_LDFLAGS="-L$withval/lib"
   fi]
 )
 
@@ -52,7 +52,7 @@ AC_ARG_WITH(cxsc-include,
     Location at which the cxsc include files were installed.],
  [CXSC=yes
   CXSC_WITH="$CXSC_WITH --with-cxsc-include=$withval"
-  CXSC_CFLAGS="-I$withval"]
+  CXSC_CPPFLAGS="-I$withval"]
 )
 
 AC_ARG_WITH(cxsc-lib,
@@ -72,7 +72,7 @@ if test "$CXSC" != extern; then
 
 AC_LANG_PUSH([C++])
 temp_status=true
-CPPFLAGS="$CPPFLAGS $CXSC_CFLAGS"
+CPPFLAGS="$CPPFLAGS $CXSC_CPPFLAGS"
 AC_CHECK_HEADER(real.hpp,,[temp_status=false])
 LDFLAGS="$LDFLAGS $CXSC_LDFLAGS"
 AC_CHECK_LIB(cxsc,z_zadd,,[temp_status=false])
@@ -93,7 +93,7 @@ fi
 if test "$CXSC" = extern; then
 
 MAKE_LIBTARGETS="$MAKE_LIBTARGETS cxsc"
-CXSC_CFLAGS='-I$(EXTERN)/include'
+CXSC_CPPFLAGS='-I$(EXTERN)/include'
 CXSC_LDFLAGS='-L$(EXTERN)/lib'
 
 CXSC_WITH='--with-cxsc=$(EXTERN)'
@@ -110,7 +110,7 @@ LIBS="$temp_LIBS"
 if test "$CXSC" != no; then
     AC_DEFINE([USE_CXSC],1,[use CXSC library])
 fi
-AC_SUBST(CXSC_CFLAGS)
+AC_SUBST([CXSC_CPPFLAGS])
 AC_SUBST(CXSC_LDFLAGS)
 AC_SUBST(CXSC_LIBS)
 AC_SUBST(CXSC_MAKELIB)
Index: float-0.7.3/src/Makefile.am
===================================================================
--- float-0.7.3.orig/src/Makefile.am
+++ float-0.7.3/src/Makefile.am
@@ -48,7 +48,7 @@ endif ## WITH_MPFR_IS_YES
 
 if WITH_CXSC_IS_YES
 float_la_SOURCES +=	cxsc.C cxsc_poly.C
-float_la_CFLAGS += $(CXSC_CFLAGS)
+float_la_CPPFLAGS += $(CXSC_CPPFLAGS)
 float_la_LDFLAGS += $(CXSC_LDFLAGS)
 float_la_LIBADD += $(CXSC_LIBS)
 endif