Using special characters (quote / space) in compiler-related variables

[Dmitry Katsubo]

Dear autoconf users/developers,

I have the following question concerning the use of special characters
in variables. After reading the documentation chapter [1], I've come to
the conclusion, that I cannot define the following in configure.ac:

CXXFLAGS="-D__int64=\"long long\" ${CXXFLAGS}"
AC_CHECK_HEADER([jni.h])

The result is:

> configure:4104: checking jni.h usability
> configure:4104: g++ -c -D__int64="long long" -g -O2 
> -I/usr/lib/jvm/java-6-sun/include -I/usr/lib/jvm/java-6-sun/include/linux 
> -I/usr/lib/jvm/java-6-sun/include/win32 -I/usr/local/include  conftest.cpp >&5
> g++: long": No such file or directory
> <command-line>: warning: missing terminating " character
> configure:4104: $? = 1

Even tough the variable is correctly set and can be used in Makefile,
but AC_CHECK_HEADER() fails to treat special characters properly.

I have also tried:

CXXFLAGS="-D__int64=long\ long" ${CXXFLAGS}"

with negative result. However I've seen some examples, where it looks to
work ([2], [3], [4]).

Maybe somebody can give me a hint, how to correctly set CXXFLAGS?
Thanks in advance!

Additional info:

autoconf 2.67 (Debian [squeeze])

> [1] 
> http://www.gnu.org/software/autoconf/manual/html_node/Special-Chars-in-Variables.html
> [2] https://developer.brewmp.com/forum/dll-gnu-auto-tools-0
> [3] http://code.google.com/p/beagle-lib/source/browse/trunk/configure.ac?r=991
> [4] http://ptolemy.berkeley.edu/java/ptplot5.8/configure

-- 
With best regards,
Dmitry