https://gcc.gnu.org/bugzilla/show_bug.cgi?id=91993
Jakub Jelinek <jakub at gcc dot gnu.org> changed:
What |Removed |Added
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CC| |jakub at gcc dot gnu.org
--- Comment #3 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
The sanitization boils down to adding COMPOUND_EXPRs with the checking in the
first operand and whatever it would normally have in the second operand.
using uc = unsigned char;
auto
foo (const uc &a, const uc &b, const uc &c)
{
return static_cast<uc>(static_cast<uc>(a << 1U) | b) | c;
}
auto
bar (const uc &a, const uc &b, const uc &c, int &d)
{
return static_cast<uc>(static_cast<uc>((d++, a) << 1U) | b) | c;
}
warns in bar the same even with just -Wconversion and doesn't warn in foo.
Now, I wonder if a way out of this wouldn't be in cp_build_binary_op to look
through COMPOUND_EXPRs (say set some temporary to (not sure if op0 or
orig_op0),
and then while (TREE_CODE (op0) == COMPOUND_EXPR) op0 = TREE_OPERAND (op0, 1);
and similarly for op1 (or orig_op1?) and then at the end readd the lhs's from
the COMPOUND_EXPRs to the result (guess for doing_shift case and
flag_strong_eval_order == 2 we'd need to either not do that or be extra
careful, because in that case op0 is ordered before op1).
Thoughts on this?
