The preprocessor will report warnings when there is an unterminated ' or " in a disabled section.
Example code that triggers two warnings: **** Code begin **** #if 0 This shouln"t cause a problem. This shouln't cause a problem. #endif int main() { return 0; } **** Code end **** Output from the preprocessor: $ cpp-4.2 -v -save-temps bug.cpp Using built-in specs. Target: i486-linux-gnu Configured with: ../src/configure -v --enable-languages=c,c++,fortran,objc,obj-c++,treelang --prefix=/usr --enable-shared --with-system-zlib --libexecdir=/usr/lib --without-included-gettext --enable-threads=posix --enable-nls --with-gxx-include-dir=/usr/include/c++/4.2 --program-suffix=-4.2 --enable-clocale=gnu --enable-libstdcxx-debug --enable-mpfr --enable-targets=all --disable-werror --enable-checking=release --build=i486-linux-gnu --host=i486-linux-gnu --target=i486-linux-gnu Thread model: posix gcc version 4.2.1 20070528 (prerelease) (Ubuntu 4.2-20070528-0ubuntu2) /usr/lib/gcc/i486-linux-gnu/4.2.1/cc1plus -E -quiet -v -D_GNU_SOURCE bug.cpp -mtune=generic -fpch-preprocess ignoring nonexistent directory "/usr/local/include/i486-linux-gnu" ignoring nonexistent directory "/usr/lib/gcc/i486-linux-gnu/4.2.1/../../../../i486-linux-gnu/include" ignoring nonexistent directory "/usr/include/i486-linux-gnu" #include "..." search starts here: #include <...> search starts here: /usr/include/c++/4.2 /usr/include/c++/4.2/i486-linux-gnu /usr/include/c++/4.2/backward /usr/local/include /usr/lib/gcc/i486-linux-gnu/4.2.1/include /usr/include End of search list. # 1 "bug.cpp" # 1 "<built-in>" # 1 "<command-line>" # 1 "bug.cpp" bug.cpp:2:12: warning: missing terminating " character bug.cpp:3:12: warning: missing terminating ' character int main() { return 0; } -- Summary: Incorrect warnings in disabled code. Product: gcc Version: 4.2.1 Status: UNCONFIRMED Severity: minor Priority: P3 Component: preprocessor AssignedTo: unassigned at gcc dot gnu dot org ReportedBy: pcmoen at gmail dot com http://gcc.gnu.org/bugzilla/show_bug.cgi?id=32271