https://gcc.gnu.org/bugzilla/show_bug.cgi?id=116182
Bug ID: 116182
Summary: bootstrap-lto should set a small list of -Werror
options for LTO correctness
(-Werror=lto-type-mismatch,odr,strict-aliasing)
Product: gcc
Version: 15.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: other
Assignee: unassigned at gcc dot gnu.org
Reporter: sjames at gcc dot gnu.org
CC: arsen at gcc dot gnu.org
Target Milestone: ---
With LTO, we have -Wlto-type-mismatch and -Wodr as powerful ways to find UB
which may explode at runtime with LTO especially.
In Gentoo, we encourage strongly that if anyone uses LTO, they use
-Werror=lto-type-mismatch,odr,strict-aliasing. We hit occasional bootstrap
issues where such a warning was missed in GCC itself, e.g. PR108087, PR115917,
PR114529, PR116181.
I'd suggest we add these 3 as -Werror= to the bootstrap-lto configuration.
I think --enable-werror is orthogonal to this because:
a) it'll make various bits like unused variables error out;
b) the pesky middle-end warnings like -Wstringop-overflow do fire during LTO
bootstraps
(I know -Wstrict-aliasing is imperfect but IME it's at least good enough in
terms of FPs for this.)
