https://gcc.gnu.org/bugzilla/show_bug.cgi?id=51628
--- Comment #54 from hjl at gcc dot gnu.org <hjl at gcc dot gnu.org> --- Author: hjl Date: Thu Dec 20 21:41:48 2018 New Revision: 267313 URL: https://gcc.gnu.org/viewcvs?rev=267313&root=gcc&view=rev Log: C/C++: Add -Waddress-of-packed-member When address of packed member of struct or union is taken, it may result in an unaligned pointer value. This patch adds -Waddress-of-packed-member to check alignment at pointer assignment and warn unaligned address as well as unaligned pointer: $ cat x.i struct pair_t { char c; int i; } __attribute__ ((packed)); extern struct pair_t p; int *addr = &p.i; $ gcc -O2 -S x.i x.i:8:13: warning: taking address of packed member of ‘struct pair_t’ may result in an unaligned pointer value [-Waddress-of-packed-member] 8 | int *addr = &p.i; | ^ $ cat c.i struct B { int i; }; struct C { struct B b; } __attribute__ ((packed)); long* g8 (struct C *p) { return p; } $ gcc -O2 -S c.i -Wno-incompatible-pointer-types c.i: In function ‘g8’: c.i:4:18: warning: converting a packed ‘struct C *’ pointer (alignment 1) to ‘long int *’ (alignment 8) may may result in an unaligned pointer value [-Waddress-of-packed-member] 4 | long* g8 (struct C *p) { return p; } | ^ c.i:2:8: note: defined here 2 | struct C { struct B b; } __attribute__ ((packed)); | ^ $ This warning is enabled by default. Since read_encoded_value_with_base in unwind-pe.h has union unaligned { void *ptr; unsigned u2 __attribute__ ((mode (HI))); unsigned u4 __attribute__ ((mode (SI))); unsigned u8 __attribute__ ((mode (DI))); signed s2 __attribute__ ((mode (HI))); signed s4 __attribute__ ((mode (SI))); signed s8 __attribute__ ((mode (DI))); } __attribute__((__packed__)); _Unwind_Internal_Ptr result; and GCC warns: gcc/libgcc/unwind-pe.h:210:37: warning: taking address of packed member of 'union unaligned' may result in an unaligned pointer value [-Waddress-of-packed-member] result = (_Unwind_Internal_Ptr) u->ptr; ^ we need to add GCC pragma to ignore -Waddress-of-packed-member. gcc/ PR c/51628 * doc/invoke.texi: Document -Wno-address-of-packed-member. gcc/c-family/ PR c/51628 * c-common.h (warn_for_address_or_pointer_of_packed_member): New. * c-warn.c (check_alignment_of_packed_member): New function. (check_address_of_packed_member): Likewise. (check_and_warn_address_of_packed_member): Likewise. (warn_for_address_or_pointer_of_packed_member): Likewise. * c.opt: Add -Wno-address-of-packed-member. gcc/c/ PR c/51628 * c-typeck.c (convert_for_assignment): Call warn_for_address_or_pointer_of_packed_member. gcc/cp/ PR c/51628 * call.c (convert_for_arg_passing): Call warn_for_address_or_pointer_of_packed_member. * typeck.c (convert_for_assignment): Likewise. gcc/testsuite/ PR c/51628 * c-c++-common/pr51628-1.c: New test. * c-c++-common/pr51628-2.c: Likewise. * c-c++-common/pr51628-3.c: Likewise. * c-c++-common/pr51628-4.c: Likewise. * c-c++-common/pr51628-5.c: Likewise. * c-c++-common/pr51628-6.c: Likewise. * c-c++-common/pr51628-7.c: Likewise. * c-c++-common/pr51628-8.c: Likewise. * c-c++-common/pr51628-9.c: Likewise. * c-c++-common/pr51628-10.c: Likewise. * c-c++-common/pr51628-11.c: Likewise. * c-c++-common/pr51628-12.c: Likewise. * c-c++-common/pr51628-13.c: Likewise. * c-c++-common/pr51628-14.c: Likewise. * c-c++-common/pr51628-15.c: Likewise. * c-c++-common/pr51628-26.c: Likewise. * c-c++-common/pr51628-27.c: Likewise. * c-c++-common/pr51628-28.c: Likewise. * c-c++-common/pr51628-29.c: Likewise. * c-c++-common/pr51628-30.c: Likewise. * c-c++-common/pr51628-31.c: Likewise. * c-c++-common/pr51628-32.c: Likewise. * gcc.dg/pr51628-17.c: Likewise. * gcc.dg/pr51628-18.c: Likewise. * gcc.dg/pr51628-19.c: Likewise. * gcc.dg/pr51628-20.c: Likewise. * gcc.dg/pr51628-21.c: Likewise. * gcc.dg/pr51628-22.c: Likewise. * gcc.dg/pr51628-23.c: Likewise. * gcc.dg/pr51628-24.c: Likewise. * gcc.dg/pr51628-25.c: Likewise. * c-c++-common/asan/misalign-1.c: Add -Wno-address-of-packed-member. * c-c++-common/asan/misalign-2.c: Likewise. * c-c++-common/ubsan/align-2.c: Likewise. * c-c++-common/ubsan/align-4.c: Likewise. * c-c++-common/ubsan/align-6.c: Likewise. * c-c++-common/ubsan/align-7.c: Likewise. * c-c++-common/ubsan/align-8.c: Likewise. * c-c++-common/ubsan/align-10.c: Likewise. * g++.dg/ubsan/align-2.C: Likewise. * gcc.target/i386/avx512bw-vmovdqu16-2.c: Likewise. * gcc.target/i386/avx512f-vmovdqu32-2.c: Likewise. * gcc.target/i386/avx512f-vmovdqu64-2.c: Likewise. * gcc.target/i386/avx512vl-vmovdqu16-2.c: Likewise. * gcc.target/i386/avx512vl-vmovdqu32-2.c: Likewise. * gcc.target/i386/avx512vl-vmovdqu64-2.c: Likewise. libgcc/ * unwind-pe.h (read_encoded_value_with_base): Add GCC pragma to ignore -Waddress-of-packed-member. Added: trunk/gcc/testsuite/c-c++-common/pr51628-1.c trunk/gcc/testsuite/c-c++-common/pr51628-10.c trunk/gcc/testsuite/c-c++-common/pr51628-11.c trunk/gcc/testsuite/c-c++-common/pr51628-12.c trunk/gcc/testsuite/c-c++-common/pr51628-13.c trunk/gcc/testsuite/c-c++-common/pr51628-14.c trunk/gcc/testsuite/c-c++-common/pr51628-15.c trunk/gcc/testsuite/c-c++-common/pr51628-16.c trunk/gcc/testsuite/c-c++-common/pr51628-2.c trunk/gcc/testsuite/c-c++-common/pr51628-26.c trunk/gcc/testsuite/c-c++-common/pr51628-27.c trunk/gcc/testsuite/c-c++-common/pr51628-28.c trunk/gcc/testsuite/c-c++-common/pr51628-29.c trunk/gcc/testsuite/c-c++-common/pr51628-3.c trunk/gcc/testsuite/c-c++-common/pr51628-30.c trunk/gcc/testsuite/c-c++-common/pr51628-31.c trunk/gcc/testsuite/c-c++-common/pr51628-32.c trunk/gcc/testsuite/c-c++-common/pr51628-4.c trunk/gcc/testsuite/c-c++-common/pr51628-5.c trunk/gcc/testsuite/c-c++-common/pr51628-6.c trunk/gcc/testsuite/c-c++-common/pr51628-7.c trunk/gcc/testsuite/c-c++-common/pr51628-8.c trunk/gcc/testsuite/c-c++-common/pr51628-9.c trunk/gcc/testsuite/gcc.dg/pr51628-17.c trunk/gcc/testsuite/gcc.dg/pr51628-18.c trunk/gcc/testsuite/gcc.dg/pr51628-19.c trunk/gcc/testsuite/gcc.dg/pr51628-20.c trunk/gcc/testsuite/gcc.dg/pr51628-21.c trunk/gcc/testsuite/gcc.dg/pr51628-22.c trunk/gcc/testsuite/gcc.dg/pr51628-23.c trunk/gcc/testsuite/gcc.dg/pr51628-24.c trunk/gcc/testsuite/gcc.dg/pr51628-25.c Modified: trunk/gcc/ChangeLog trunk/gcc/c-family/ChangeLog trunk/gcc/c-family/c-common.h trunk/gcc/c-family/c-warn.c trunk/gcc/c-family/c.opt trunk/gcc/c/ChangeLog trunk/gcc/c/c-typeck.c trunk/gcc/cp/ChangeLog trunk/gcc/cp/call.c trunk/gcc/cp/typeck.c trunk/gcc/doc/invoke.texi trunk/gcc/testsuite/ChangeLog trunk/gcc/testsuite/c-c++-common/asan/misalign-1.c trunk/gcc/testsuite/c-c++-common/asan/misalign-2.c trunk/gcc/testsuite/c-c++-common/ubsan/align-10.c trunk/gcc/testsuite/c-c++-common/ubsan/align-2.c trunk/gcc/testsuite/c-c++-common/ubsan/align-4.c trunk/gcc/testsuite/c-c++-common/ubsan/align-6.c trunk/gcc/testsuite/c-c++-common/ubsan/align-7.c trunk/gcc/testsuite/c-c++-common/ubsan/align-8.c trunk/gcc/testsuite/g++.dg/ubsan/align-2.C trunk/gcc/testsuite/gcc.target/i386/avx512bw-vmovdqu16-2.c trunk/gcc/testsuite/gcc.target/i386/avx512f-vmovdqu32-2.c trunk/gcc/testsuite/gcc.target/i386/avx512f-vmovdqu64-2.c trunk/gcc/testsuite/gcc.target/i386/avx512vl-vmovdqu16-2.c trunk/gcc/testsuite/gcc.target/i386/avx512vl-vmovdqu32-2.c trunk/gcc/testsuite/gcc.target/i386/avx512vl-vmovdqu64-2.c trunk/libgcc/ChangeLog trunk/libgcc/unwind-pe.h
