Given the following test case: #define f(x, y) "x y"
extern void abort (void); int main () { const char *str1 = f("a", "\"a\""); const char *str2 = f( \t, " \t"); if (strcmp (str1, "\"a\" \"\\\"a\\\"\"")) abort (); if (strcmp (str2, "\t \" \\t\"")) abort (); return 0; } Gcc 2.95.3 will accept it and do the right thing: $ gcc -v Reading specs from /opt/local/fsf/lib/gcc-lib/i686-pc-linux-gnu/2.95.3/specs gcc version 2.95.3 20010315 (release) $ gcc -traditional-cpp -o macroargs macroargs.c $ ./macroargs $ Current gcc 4.X fails to accept this code. For example, using the Fedora Core 6 compiler: $ /usr/bin/gcc -v Using built-in specs. Target: i386-redhat-linux Configured with: ../configure --prefix=/usr --mandir=/usr/share/man --infodir=/usr/share/info --enable-shared --enable-threads=posix --enable-checking=release --with-system-zlib --enable-__cxa_atexit --disable-libunwind-exceptions --enable-libgcj-multifile --enable-languages=c,c++,objc,obj-c++,java,fortran,ada --enable-java-awt=gtk --disable-dssi --enable-plugin --with-java-home=/usr/lib/jvm/java-1.4.2-gcj-1.4.2.0/jre --with-cpu=generic --host=i386-redhat-linux Thread model: posix gcc version 4.1.1 20061011 (Red Hat 4.1.1-30) $ /usr/bin/gcc -traditional-cpp -o macroargs macroargs.c macroargs.c: In function main: macroargs.c:7: error: expected , or ; before a macroargs.c:7: error: stray \ in program macroargs.c:7: error: missing terminating " character macroargs.c:8: error: stray \ in program macroargs.c:12: error: str2 undeclared (first use in this function) macroargs.c:12: error: (Each undeclared identifier is reported only once macroargs.c:12: error: for each function it appears in.) The attached patch (also posted to gcc-patches) will fix it, although it's handling of quoted arguments is not exactly identical to gcc 2.95.3. Notice the difference between the test case above, and the test case included with the patch. Here is an example of a patched gcc's behavior: $ /opt/specifix/experimental/bin/gcc -v Using built-in specs. Target: i686-pc-linux-gnu Configured with: /src/specifix/experimental/src/gcc/configure --enable-languages=c,c++,fortran --prefix=/opt/specifix/experimental --disable-werror --disable-bootstrap --with-mpfr=/opt/specifix/experimental --with-gmp=/opt/specifix/experimental --cache-file=/dev/null --srcdir=/src/specifix/experimental/src/gcc Thread model: posix gcc version 4.3.0 20061231 (experimental) $ /opt/specifix/experimental/bin/gcc -traditional-cpp -o macroargs macroargs.c $ Note however that the above test case WILL abort if run, while the test case included with the patch will not, due to the handling of leading and trailing whitespace in macro args. See the code inside "#if 0 ... #endif" in the patch and the associated comments. Either the current gcc testsuite is wrong in how it tests for this whitespace, or gcc 2.95.3 is wrong. It's not clear to me which behavior is more correct. -- Summary: Support for -traditional-cpp is incomplete in current gcc relative to gcc 2.95.3 Product: gcc Version: 4.3.0 Status: UNCONFIRMED Severity: normal Priority: P3 Component: preprocessor AssignedTo: unassigned at gcc dot gnu dot org ReportedBy: fnf at specifixinc dot com GCC build triplet: i686-pc-linux-gnu GCC host triplet: i686-pc-linux-gnu GCC target triplet: i686-pc-linux-gnu http://gcc.gnu.org/bugzilla/show_bug.cgi?id=30363