Ping: https://gcc.gnu.org/ml/gcc-patches/2017-07/msg00036.html
On 07/02/2017 02:00 PM, Martin Sebor wrote:
The attached patch enhances the -Wrestrict warning to detect more than just trivial instances of overlapping copying by sprintf and related functions. The meat of the patch is relatively simple but because it introduces dependencies between existing classes in the sprintf pass I had to move the class definitions around. That makes the changes look more extensive than they really are. The enhancement works by first determining the base object (or pointer) from the destination of the sprintf call, the constant offset into the object, and its size. For each %s argument, it then computes same information. If it determines that overlap between the two is possible it stores the information for the directive argument (including the size of the argument) for later processing. After the whole call/format string has been processed, the patch then iterates over the stored directives and their arguments and compares the size/length of the argument against the function's overall output. If they overlap it issues a warning. Tested on x86_64-linux. -Wrestrict is not currently included in either -Wextra or -Wall and this patch doesn't change it even though there have been requests to add it to one of these two options. I'd like to do that as a separate step. As the next step I'd also like to extend a limited form of the -Wrestrict enhancement to other restrict-qualified built-ins (like strcpy), and ultimately also to user-defined functions that make use of restrict. I think this might perhaps best be done in a separate pass where the computed pointer information can be cached to avoid recomputing it for each call, but I don't expect to be able to have the new pass (or whatever form the enhancement might end up taking) to also handle sprintf (at least not with the same accuracy it does now) because the sprintf data for each format directive are not available outside the sprintf pass. Martin
