C++ programs with "if (NULL)" generate an unpleasant warning even with default compiler options. Code with "if (NULL)" comes from of macro expansion or auto-generated code.
Warnings are a matter of taste so I won't ask "make all the warnings match my taste", but I do petition you to revisit which of these lines should generate warnings and apply your own taste. This patch looks like the last time these warnings were modified: http://gcc.gnu.org/ml/gcc-patches/2005-01/msg02230.html Mark Mitchell, C++ PATCH: PR 19457 a PR 19349 Test program: int foo() { if (__null) return -1; if (!__null) ; else return -1; if (__null == __null) ; else return -1; if (__null != __null) return -1; if (__null == __null) ; else return -1; if (__null != 0) ; else return -1; return 0; } int main() { return foo() == 0; } Warnings shown: hollerith:~/null-arithmetic$ /home/mec/gcc-4.0.2/install/bin/gcc -c null-arithmetic.cc null-arithmetic.cc: In function 'int foo()': null-arithmetic.cc:2: warning: converting to non-pointer type 'bool' from NULL null-arithmetic.cc:3: warning: converting to non-pointer type 'bool' from NULL null-arithmetic.cc:4: warning: NULL used in arithmetic null-arithmetic.cc:5: warning: NULL used in arithmetic null-arithmetic.cc:6: warning: NULL used in arithmetic null-arithmetic.cc:7: warning: NULL used in arithmetic hollerith:~/null-arithmetic$ /home/mec/gcc-4.1-20051105/install/bin/gcc -c null-arithmetic.cc null-arithmetic.cc: In function 'int foo()': null-arithmetic.cc:2: warning: converting to non-pointer type 'bool' from NULL null-arithmetic.cc:3: warning: converting to non-pointer type 'bool' from NULL null-arithmetic.cc:4: warning: NULL used in arithmetic null-arithmetic.cc:5: warning: NULL used in arithmetic null-arithmetic.cc:6: warning: NULL used in arithmetic null-arithmetic.cc:7: warning: NULL used in arithmetic -- Summary: unpleasant warning for "if (NULL)" Product: gcc Version: 4.0.2 Status: UNCONFIRMED Severity: minor Priority: P3 Component: c++ AssignedTo: unassigned at gcc dot gnu dot org ReportedBy: mec at google 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=24745
