[PATCH] clang-tidy: check for repeated side effects in macro

[Daniel Marjamäki]

This is a new clang-tidy checker that warns when there is side effects in a macro argument that is repeated in the macro expansion.

I am running tests. Right now it has been tested on 7678 files in 180 projects. And there has been in total 7 warnings. As far as I see all these 7 warnings are real bugs.

Interestingly I get a couple of warnings for standard functions that are implemented as macros. As far as I see my headers are not standard-compliant:

format.c:774:28: warning: Side effects in macro argument is repeated in macro expansion [misc-macro-repeated-side-effects]
                tblt->instr[0] = toupper(*p++);
                                         ^
/usr/include/ctype.h:229:11: note: 'toupper' macro defined here
#  define toupper(c)    __tobody (c, toupper, *__ctype_toupper_loc (), (c))
          ^

tunnel.c:73:25: warning: Side effects in macro argument is repeated in macro expansion [misc-macro-repeated-side-effects]
      char *q = strchr (++p, '"');
                        ^
/usr/include/x86_64-linux-gnu/bits/string2.h:395:11: note: 'strchr' macro defined here
#  define strchr(s, c) \
  (__extension__ (__builtin_constant_p (c) && !__builtin_constant_p (s)	      \
		  && (c) == '\0'					      \
		  ? (char *) __rawmemchr (s, c)				      \
		  : __builtin_strchr (s, c)))

...

http://reviews.llvm.org/D9496

Files:
  clang-tidy/misc/CMakeLists.txt
  clang-tidy/misc/MacroRepeatedSideEffectsCheck.cpp
  clang-tidy/misc/MacroRepeatedSideEffectsCheck.h
  clang-tidy/misc/MiscTidyModule.cpp
  test/clang-tidy/misc-repeated-side-effects-in-macro.c

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