For ``` .size foo1, 1 foo1: .set bar1, foo1 .size bar1, 2 .size bar2, 2 .set bar2, foo1 .set bar3, foo2 .size bar3, 2 .size bar4, 2 .set bar4, foo2 .size foo2, 1 foo2: ``` bar1's size is 2 while bar2, bar3, bar4's is 1. The behavior of bar1 makes sense (generally directives on the new symbol should win) and is relied upon by glibc stdio-common/errlist.c: ``` .hidden _sys_errlist_internal .globl _sys_errlist_internal .type _sys_errlist_internal, @object .size _sys_errlist_internal, 1072 _sys_errlist_internal: .globl __GLIBC_2_1_sys_errlist .set __GLIBC_2_1_sys_errlist, _sys_errlist_internal .type __GLIBC_2_1_sys_errlist, %object .size __GLIBC_2_1_sys_errlist, 125 * (64 / 8) // glibc expects that .size __GLIBC_2_1_sys_errlist, 125 * (64 / 8) wins. ``` The behavior of bar2/bar3/bar4 seems brittle. To avoid the reordering of the two code blocks which will result in the bar3 situation, glibc compiles errlist.c with gcc -fno-toplevel-reorder (previously -fno-unit-at-a-time). To fix the inconsistency and improve robustness, I think we should make bar2/bar3/bar4 match bar1, removing the directive order sensitivity. There is a pity that `.size dest, 0` is indistinguishable from the case where dest is unset, but it should be fine.
PATCH: https://sourceware.org/pipermail/binutils/2022-March/120299.html LLVM integrated assembler has had a similar behavior since 2014-03: https://github.com/llvm/llvm-project/commit/a041ef1bd8905f0d58e301c6830b183002ff1847#diff-5f22c59676e12f7ca563d9e9324c35c9e66523e9b21a91c91fe5c73ddd09fe6aR642
The master branch has been updated by Fangrui Song <maskray@sourceware.org>: https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;h=867b8c308a40e79f90db4051cafc273f00f881fb commit 867b8c308a40e79f90db4051cafc273f00f881fb Author: Fangrui Song <i@maskray.me> Date: Mon Apr 4 08:43:50 2022 -0700 gas: copy st_size only if unset For ``` .size foo1, 1 foo1: .set bar1, foo1 .size bar1, 2 .size bar2, 2 .set bar2, foo1 .set bar3, foo2 .size bar3, 2 .size bar4, 2 .set bar4, foo2 .size foo2, 1 foo2: ``` bar1's size is 2 while bar2, bar3, bar4's is 1. The behavior of bar1 makes sense (generally directives on the new symbol should win) and is relied upon by glibc stdio-common/errlist.c: ``` .hidden _sys_errlist_internal .globl _sys_errlist_internal .type _sys_errlist_internal, @object .size _sys_errlist_internal, 1072 _sys_errlist_internal: .globl __GLIBC_2_1_sys_errlist .set __GLIBC_2_1_sys_errlist, _sys_errlist_internal .type __GLIBC_2_1_sys_errlist, %object .size __GLIBC_2_1_sys_errlist, 125 * (64 / 8) // glibc expects that .size __GLIBC_2_1_sys_errlist, 125 * (64 / 8) wins. ``` The behavior of bar2/bar3/bar4 seems brittle. To avoid the reordering of the two code blocks which will result in the bar3 situation, glibc compiles errlist.c with gcc -fno-toplevel-reorder (previously -fno-unit-at-a-time). To fix the inconsistency and improve robustness, make bar2/bar3/bar4 match bar1, removing the directive order sensitivity. There is a pity that `.size dest, 0` is indistinguishable from the case where dest is unset, but the compromise seems fine. PR gas/29012 * config/obj-elf.c (elf_copy_symbol_attributes): don't copy if src's size has been set. * testsuite/gas/elf/elf.exp: New test. * testsuite/gas/elf/size.d: New file. * testsuite/gas/elf/size.s: Likewise.
Target milestone: 2.39