PING [PATCH] add access warning pass

[Martin Sebor <msebor@gmail.com>]

Ping: https://gcc.gnu.org/pipermail/gcc-patches/2021-July/575377.html

On 7/15/21 4:39 PM, Martin Sebor wrote:
> A number of access warnings as well as their supporting
> infrastructure (compute_objsize et al.) are implemented in
> builtins.{c,h} where they  (mostly) operate on trees and run
> just before RTL expansion.
> 
> This setup may have made sense initially when the warnings were
> very simple and didn't perform any CFG analysis, but it's becoming
> a liability.  The code has grown both in size and in complexity,
> might need to examine the CFG to improve detection, and in some
> cases might achieve a better S/R ratio if run earlier.  Running
> the warning code on trees is also slower because it doesn't
> benefit from the SSA_NAME caching provided by the pointer_query
> class.  Finally, having the code there is also an impediment to
> maintainability as warnings and builtin expansion are unrelated
> to each other and contributors to one area shouldn't need to wade
> through unrelated code (similar for patch reviewers).
> 
> The attached change introduces a new warning pass and a couple of
> new source and headers and, as the first step, moves the warning
> code from builtins.{c,h} there.  To keep the initial changes as
> simple as possible the pass only runs a subset of existing
> warnings: -Wfree-nonheap-object, -Wmismatched-dealloc, and
> -Wmismatched-new-delete.  The others (-Wstringop-overflow and
> -Wstringop-overread) still run on the tree representation and
> are still invoked from builtins.c or elsewhere.
> 
> The changes have no functional impact either on codegen or on
> warnings.  I tested them on x86_64-linux.
> 
> As the next step I plan to change the -Wstringop-overflow and
> -Wstringop-overread code to run on the GIMPLE IL in the new pass
> instead of on trees in builtins.c.
> 
> Martin
> 
> PS The builtins.c diff produced by git diff was much bigger than
> the changes justify.  It seems that the code removal somehow
> confused it.  To make review easy I replaced it with a plain
> unified diff of builtins.c that doesn't suffer from the problem.