https://gcc.gnu.org/bugzilla/show_bug.cgi?id=99975
Bug ID: 99975 Summary: wrong variable alignment on a locally redeclared overaligned extern variable Product: gcc Version: 11.0 Status: UNCONFIRMED Severity: normal Priority: P3 Component: c++ Assignee: unassigned at gcc dot gnu.org Reporter: msebor at gcc dot gnu.org Target Milestone: --- Perhaps due to the same underlying bug as pr99974, the C++ front end determines the wrong alignment from an overaligned extern variable redeclared locally without the alignment attribute. Both the C front end as well as other compilers (Clang and ICC) behave correctly and determine the same alignment in both functions. $ cat z.C && /build/gcc-master/gcc/xgcc -B /build/gcc-master/gcc -O -S -Wall -fdump-tree-optimized=/dev/stdout z.C extern __attribute__ ((aligned (32))) int i; int fa32 () { return __alignof__ (i); // folded to 32 (good) } int ga32 () { extern int i; return __alignof__ (i); // folded to 4 (bug) } ;; Function fa32 (_Z4fa32v, funcdef_no=0, decl_uid=2347, cgraph_uid=1, symbol_order=0) int fa32 () { <bb 2> [local count: 1073741824]: return 32; } ;; Function ga32 (_Z4ga32v, funcdef_no=1, decl_uid=2349, cgraph_uid=2, symbol_order=1) int ga32 () { <bb 2> [local count: 1073741824]: return 4; }