https://gcc.gnu.org/bugzilla/show_bug.cgi?id=115185
--- Comment #15 from Alejandro Colomar <alx at kernel dot org> --- (In reply to Sergei Trofimovich from comment #14) > This generates warning on reasonably looking code. > > On strace-6.9: > https://github.com/strace/strace/blob/v6.9/src/print_utils.h#L16 > > In file included from v4l2.c:40: > print_utils.h:16:35: error: initializer-string for array of 'char' is too > long [-Werror=unterminated-string-initialization] > 16 | static const char hex_chars[16] = "0123456789abcdef"; > | ^~~~~~~~~~~~~~~~~~ This is the kind of code I'd warn about. One may be tempted to do strchr(hex_chars, *p); in a loop to parse a hex number from a string. And then bug. That would probably be triggered to easily, admittedly. Surrounding that with a pragma to turn off the warning there would let the programmer clearly know that it's not a string. > > /cc Dmitry > > On elfutils-0.191: > https://sourceware.org/git/?p=elfutils.git;a=blob;f=backends/x86_64_regs.c; > h=ef987daf43f01187c468d29e4d412ecafdcb2878; > hb=18a015c0b0787ba5acb39801ab7c17dac50f584d#l85 > > x86_64_regs.c: In function 'x86_64_register_info': > x86_64_regs.c:85:11: error: initializer-string for array of 'char' is too > long [-Werror=unterminated-string-initialization] > 85 | "ax", "dx", "cx", "bx", "si", "di", "bp", "sp > | ^~~~ > > /cc Mark > > I would say both uses are reasonable even if they strip trailing '\0'. Agree, which is why I didn't include it in Wall. > > Warning-free code that does the equivalent might be a bit ugly: > > static const char hex_chars[17] = "0123456789abcdef"; // extra byte > > or > > static const char hex_chars[16] = { '0', '1', ..., 'f' }; // lots of > boilerplate Agree, I don't like the workarounds. Maybe a project that does that often would better use -Wno-unterminated-string-initialization, or if it's only sporadically, use a pragma around the specific uses. > > WDYT of relaxing gcc warning a bit and not complain if the only thing it > strips is a '\0'? That's precisely the purpose of that warning: warn when it's an off-by-one, so the '\0' is removed. When it's an off-by-two-or-more, it's a (pedantic) error: $ cat offbytwo.c char x[2] = "foo"; $ cc offbytwo.c -S offbytwo.c:1:13: warning: initializer-string for array of ‘char’ is too long 1 | char x[2] = "foo"; | ^~~~~ $ cc offbytwo.c -pedantic-errors -S offbytwo.c:1:13: error: initializer-string for array of ‘char’ is too long 1 | char x[2] = "foo"; | ^~~~~ > Otherwise at least strace and elfutils would have to adapt. The only option I would see is to not enable this in -Wextra. But I think the implicit contract with -Wextra is that you want this kind of warnings that are often useful but sometimes not.
