On 1/6/2012 04:42, Kai Tietz wrote: > 2012/1/5 Christian Franke <[email protected]>: >> [Originally sent to Cygwin mailing list] >> >> When printf/scanf functions from MinGW runtime are selected via >> __USE_MINGW_ANSI_STDIO, then format string checking is broken. This only >> affects the C++ compiler: >> >> $ cygcheck -f /usr/bin/i686-w64-mingw32-g++ >> mingw64-i686-gcc-g++-4.5.3-4 >> >> $ cat testfmt.c >> #define __USE_MINGW_ANSI_STDIO 1 >> #include <stdio.h> >> >> void myprintf(const char *, ...) >> __attribute__((format(gnu_printf,1,2))); >> >> int main() >> { >> long long x = 42; >> printf("%lld\n", x); // C++: Bogus warning >> myprintf("%lld\n", x); // No warning (OK) >> printf("%I64d\n", x); // Warning (OK) >> return 0; >> } >> >> $ i686-w64-mingw32-gcc -Wformat -c testfmt.c >> testfmt.c: In function 'main': >> testfmt.c:12:3: warning: format '%I64d' expects type 'int', but argument >> 2 has type 'long long int' >> >> $ i686-w64-mingw32-g++ -Wformat -c testfmt.c >> testfmt.c: In function 'int main()': >> testfmt.c:10:21: warning: unknown conversion type character 'l' in format >> testfmt.c:10:21: warning: too many arguments for format >> testfmt.c:12:22: warning: format '%I64d' expects type 'int', but >> argument 2 has type 'long long int' >> >> >> Interestingly the bogus warning only occurs for standard functions like >> printf(). These are replaced by inline functions in MinGW stdio.h if >> __USE_MINGW_ANSI_STDIO is set. Probably a subtle bug in the handling of >> functions known by the compiler. > > Issue is fixed on trunk. Version 2 branch still has those issues, as > fixes to stdio.h and wchar.h were not merged back. >
Looks like I need to do a new header/crt release soon. >> Downgrading to previous version fixes the problem: >> >> $ cygcheck -f /usr/bin/i686-w64-mingw32-g++ >> mingw64-i686-gcc-g++-4.5.3-3 >> >> $ i686-w64-mingw32-g++ -Wformat -c testfmt.c >> testfmt.c: In function 'int main()': >> testfmt.c:12:22: warning: format '%I64d' expects type 'int', but >> argument 2 has type 'long long int' >> >> >> Another observation: Include files from C++ standard library (e.g. >> <string>) now silently set __USE_MINGW_ANSI_STDIO: >> >> /usr/lib/gcc/i686-w64-mingw32/4.5.3/include/c++/i686-w64-mingw32/bits/os_defines.h: >> >> ... >> #undef __USE_MINGW_ANSI_STDIO >> #define __USE_MINGW_ANSI_STDIO 1 >> >> Is this done to ensure that iostream templates use the correct >> FILE/stdio version? >> (This was also not present in previous version 4.5.3-3). > > Yes, this fixes internal libstdc++ usage of printf/scanf routines. > libstdc++ internally assumes that printf/scanf function have POSIX > semantics. So it makes no sense to make our POSIX printf/scanf > functions optional, and so I turned them on by default. To get still > MS printf routines in C++, it is recommented to use > underscored-function-name instead. > Yes, this was added deliberately in the latest version.
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