Sam, Two quick questions:
1. Do you check the return type of c_str() to make sure it matches what you expect? If you do check the type and it does not match, you should also check if the returned type has a conversion operator to the type needed. 2. Does this handle wide-character strings? I like the idea of adding this note, I think it will be helpful for many users. -Hal On Fri, 1 Jun 2012 14:59:42 -0700 Sam Panzer <[email protected]> wrote: > Hi, > > We had a request for more user-friendly printf() diagnostics, which > asked for a note suggesting a call to .c_str() when passing a c++ > string to printf when a char* is expected, and I thought it would > make a good first submission: > > Currently code such as > > > > string foo; > > > > printf("Oh dear %s", foo); > > > > produces a reasonable (if somewhat technical) diagnostic: > > > > error: cannot pass object of non-trivial type 'string' (aka > >> 'basic_string<char>') through variadic function; call will abort > >> at runtime [-Wnon-pod-varargs] > > > > printf("Oh dear %s", foo); > > > > > >> That confuses some people (such as people who happened to be > >> sitting near me today). It would be easy for them to understand > >> if this could special-case the situation where the call is to a > >> *printf-like function and the non-POD in question is a string (or > >> std::string), to suggest that the solution might be to add the > >> missing ".c_str()". > > > > > >> When format string checking is active for the function/argument in > >> question it would also be possible to report on the expected > >> argument type. > > > > > >> (Of course it's also not ideal to report that the "call will abort > >> at runtime" when generating an error rather than a warning, but > >> that might not be worth fixing.) > > > > > I attached a patch which emits this note when an object defining > a .c_str() member function is passed instead of a char*, along with a > test file. Searching for c_str() was intended to allow the note to > fire for std::string replacements. > > -Sam -- Hal Finkel Postdoctoral Appointee Leadership Computing Facility Argonne National Laboratory _______________________________________________ cfe-commits mailing list [email protected] http://lists.cs.uiuc.edu/mailman/listinfo/cfe-commits
