[Bug c++/64767] Could GCC warn when a pointer is compared against '\0'?
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=64767 --- Comment #11 from Eric Gallager --- Thank you for adding this!
[Bug c++/64767] Could GCC warn when a pointer is compared against '\0'?
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=64767 Marek Polacek changed: What|Removed |Added Status|ASSIGNED|RESOLVED Resolution|--- |FIXED --- Comment #10 from Marek Polacek --- Done for GCC 7.
[Bug c++/64767] Could GCC warn when a pointer is compared against '\0'?
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=64767 --- Comment #9 from Marek Polacek --- Author: mpolacek Date: Wed Jan 4 21:47:04 2017 New Revision: 244076 URL: https://gcc.gnu.org/viewcvs?rev=244076=gcc=rev Log: PR c++/64767 * c.opt (Wpointer-compare): New option. * c-parser.c (c_parser_postfix_expression): Mark zero character constants by setting original_type in c_expr. * c-typeck.c (parser_build_binary_op): Warn when a pointer is compared with a zero character constant. (char_type_p): New function. * typeck.c (cp_build_binary_op): Warn when a pointer is compared with a zero character literal. * doc/invoke.texi: Document -Wpointer-compare. * c-c++-common/Wpointer-compare-1.c: New test. Added: trunk/gcc/testsuite/c-c++-common/Wpointer-compare-1.c Modified: trunk/gcc/ChangeLog trunk/gcc/c-family/ChangeLog trunk/gcc/c-family/c.opt trunk/gcc/c/ChangeLog trunk/gcc/c/c-parser.c trunk/gcc/c/c-typeck.c trunk/gcc/cp/ChangeLog trunk/gcc/cp/typeck.c trunk/gcc/doc/invoke.texi trunk/gcc/testsuite/ChangeLog
[Bug c++/64767] Could GCC warn when a pointer is compared against '\0'?
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=64767 Eric Gallager changed: What|Removed |Added CC||egall at gwmail dot gwu.edu --- Comment #8 from Eric Gallager --- (In reply to Marek Polacek from comment #7) > This code is now rejected in C++11. See r240707. What about in other standards? gcc built at the end of November still seems to reject the -Wpointer-compare flag that I thought was going to be added for this: $ /usr/local/bin/gcc -Wpointer-compare randomer.c gcc: error: unrecognized command line option ‘-Wpointer-compare’; did you mean ‘-Wnonnull-compare’?
[Bug c++/64767] Could GCC warn when a pointer is compared against '\0'?
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=64767 --- Comment #7 from Marek Polacek --- This code is now rejected in C++11. See r240707.
[Bug c++/64767] Could GCC warn when a pointer is compared against '\0'?
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=64767 Marek Polacek changed: What|Removed |Added Status|NEW |ASSIGNED CC||mpolacek at gcc dot gnu.org Assignee|unassigned at gcc dot gnu.org |mpolacek at gcc dot gnu.org --- Comment #6 from Marek Polacek --- Looking into this; the C FE part will be harder than the C++ FE part since the latter has delayed folding. I'm wondering whether a warning for ptr == (char) 0 would be desirable or not, but I guess so.
[Bug c++/64767] Could GCC warn when a pointer is compared against '\0'?
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=64767 Manuel López-Ibáñez changed: What|Removed |Added CC||manu at gcc dot gnu.org --- Comment #5 from Manuel López-Ibáñez --- This could have detected a bug in GCC: http://www.viva64.com/en/b/0425/
[Bug c++/64767] Could GCC warn when a pointer is compared against '\0'?
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=64767 --- Comment #2 from Ulf Magnusson ulfalizer at gmail dot com --- Looks like -Wnon-literal-null-conversion is intended to warn for the comparison case too, though it doesn't seem to be implemented yet as of clang 3.4: http://llvm.org/klaus/clang/commit/50800fc551ac6b8a95cca662223e7f061bbd169a/
[Bug c++/64767] Could GCC warn when a pointer is compared against '\0'?
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=64767 --- Comment #3 from Ulf Magnusson ulfalizer at gmail dot com --- clang also generates a warning for C programs with void *a = '\0' by the way, so it seems to be able to look at the form of the integral constant there.
[Bug c++/64767] Could GCC warn when a pointer is compared against '\0'?
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=64767 --- Comment #4 from Jonathan Wakely redi at gcc dot gnu.org --- Yes, although C says '\0' has type int the compiler can still distinguish the token '\0' from 0 during compilation.
[Bug c++/64767] Could GCC warn when a pointer is compared against '\0'?
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=64767
Jonathan Wakely redi at gcc dot gnu.org changed:
What|Removed |Added
Status|UNCONFIRMED |NEW
Last reconfirmed||2015-01-24
Ever confirmed|0 |1
Severity|enhancement |normal
--- Comment #1 from Jonathan Wakely redi at gcc dot gnu.org ---
Confirming as a bug not an extension.
In C++03 the code is valid because pointer conversions are allowed for integral
constant expressions, such as '\0', but in C++11 pointer conversions are only
allowed for an integer-literal and not a char-literal.
So this should be an error in C++11, and adding a warning in C++03 at the same
time would make sense (maybe enabled by -Wzero-as-null-pointer-constant and/or
-Wc++11-compat)
Clang gives a hard error with -std=c++11
warn.cc:4:9: error: comparison between pointer and integer ('void *' and 'int')
if (p == '\0')
~ ^
1 error generated.
Similarly for initializing a pointer with a char-literal, for which clang gives
an error in C++11 mode, and a warning for C++98.
warn.cc:3:9: error: cannot initialize a variable of type 'void *' with an
rvalue of type 'char'
void* p = '\0';
^
1 error generated.
warn.cc:3:13: warning: expression which evaluates to zero treated as a null
pointer constant of type 'void *' [-Wnon-literal-null-conversion]
void* p = '\0';
^~~~
1 warning generated.
