On 02/21/2018 07:53 PM, Jeff Law wrote:
On 02/21/2018 02:19 PM, Martin Sebor wrote:
The attached patch eliminates -Wstringop-truncation false
positives reported in bug 84480 - bogus -Wstringop-truncation
despite assignment with an inlined string literal.  It does
that by delegating early strncpy checks during folding to
the same machinery in tree-ssa-strlen that looks for a NUL
assignment to the destination the next statement.

The patch also adds inlining context to the warnings via
the %G directive.

Tested on x86_64-linux with no regressions.



PR tree-optimization/84480 - bogus -Wstringop-truncation despite assignment 
with an inlined string literal


        PR tree-optimization/84480
        * gimple-fold.c (gimple_fold_builtin_strcpy): Move warnings
        to maybe_diag_stxncpy_trunc.  Call it.
        * tree-ssa-strlen.c (maybe_diag_stxncpy_trunc): Integrate warnings
        from gimple_fold_builtin_strcpy.  Print inlining stack.
        (handle_builtin_stxncpy): Print inlining stack.
        * tree-ssa-strlen.h (maybe_diag_stxncpy_trunc): Declare.


        PR tree-optimization/84480
        * c-c++-common/Wstringop-truncation.c: Adjust text of expected warnings.
        * g++.dg/warn/Wstringop-truncation-1.C: New test.
In general our guidelines are that the users of a .h file should include
any dependencies rather than having the .h file itself include other .h
files (Now that we've detangled the header files we may want to revisit
that guideline, but that's not a gcc-8 item).

It looks like gimple-fold.c and tree-ssa-strlen.c already have the
prereqs.  So in theory you should be able to just remove the bogus
#includes from tree-ssa-strlen.h.


In general we want to avoid adding more warnings to folding code.  But I
think the argument here is that we're already trying to warn within the
folder and just doing a poor job -- so we're removing that
implementation and delegating the warning to a better implementation.


So I think you just need to remove the bogus #includes from
tree-ssa-strlen and this is OK.

Thanks.  Committed in r257910.


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