On 08/12/2016 01:27 PM, David Malcolm wrote:
In r239260 I attempted to add fix-it hints for -Wformat type warnings.Unfortunately, my implementation was too simplistic, and only worked correctly for the most simple format strings: the fix-it hint would suggest replacement of an entire conversion specification, but the replacement would only include the length modifier (if any) and the conversion character, thus effectively discarding any user-supplied flags, width, or precision. Additionally, the replacement failed to take into account the user-specified conversion character, so that e.g. an "x" could be replaced by a "d". The following patch fixes these issues by: (a) making the suggestion retain any user-supplied part of the conversion specification before the length modifier, and (b) attempt to preserve the user-specified conversion character, by first considering replacements that only change the length modifier. It also expands the function comments in c-format.c, showing how the functions work through a non-trivial example. This patch is a followup to: "[PATCH] Fix caret locations in format_type_warning (PR c/72857)" https://gcc.gnu.org/ml/gcc-patches/2016-08/msg00867.html Successfully bootstrapped®rtested on x86_64-pc-linux-gnu (on top of the other patch).
A couple of things I noticed when getting the -Wformat-length code to use the new infrastructure from c-format. Hints that suggest alternate directives that don't accept all the same flags as those used in the original should filter out those flags. For example, when passing a pointer to a "%#lx" directive, the hint should suggest "%s" for character pointers and "%p" for others rather than "%#s" or "%#p". Similarly, when passing a string to a "%+i" or "% i" directive, the '+' and space flags should be removed. Also, with -Wformat-signedness (but I'd say without it as well), the hints should respect the signedness of the arguments. For example, the hint for "%u" with a long int argument should be "%lu" and not "%li". Martin
