https://llvm.org/bugs/show_bug.cgi?id=31888
Bug ID: 31888
Summary: assembler ELF .section type defaulted wrong for
.bss-like sections not named .bss
Product: libraries
Version: trunk
Hardware: PC
OS: Linux
Status: NEW
Severity: normal
Priority: P
Component: MC
Assignee: unassignedb...@nondot.org
Reporter: rol...@hack.frob.com
CC: llvm-bugs@lists.llvm.org, pho...@chromium.org
Classification: Unclassified
In the GNU assembler, several patterns of section name make the default
type be SHT_NOBITS if none was given explicitly in the .section directive.
LLVM's assembler does this for .bss and .tbss, but not the others.
Test case:
.text
.data
d0: .space 1
.section .bss
a: .space 1
.section .bss.foo
b: .space 1
.section .bss.bar,"aw"
b1: .space 1
.section .tbss
c: .space 1
.section .tbss.foo
d: .space 1
.section .tbss.bar,"aw"
d1: .space 1
.section .gnu.linkonce.b
e: .space 1
.section .gnu.linkonce.b.foo
f: .space 1
.section .gnu.linkonce.b.bar,"aw"
f1: .space 1
With GAS, all of these (except .text and .data) get SHT_NOBITS. The cases
with no explicit flags string SHF_ALLOC|SHF_WRITE (as if the flags string
were "aw"), and .tbss* also get SHF_TLS (as if the flags string were
"awT"). .tbss.bar also gets SHT_TLS set even though T did not appear in
the explicit flags string.
With LLVM MC, only .bss and .tbss get SHT_NOBITS and only .tbss gets
SHT_TLS. The cases with no explicit flags string (except for .bss and
.tbss) get no bits set in sh_flags.
I can see the case for not adding SHT_TLS when there was an explicit flags
string. I won't consider it a continuing bug if the .tbss.bar case fails
to add in SHF_TLS.
When the flags or type was omitted, people expect to get the defaults based
on the section name as GAS does.
I'm only looking at the SHT_NOBITS cases here. There are other cases where
GAS defines a default type and default flags based on the name. You can
see them in bfd/elf.c in the special_sections_* tables.
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