26ddf4eee2
`clang -g -gpubnames -fdebug-types-section` now emits .debug_names
section with references to local type unit entries defined in COMDAT
.debug_info sections.
```
.section .debug_info,"G",@progbits,5657452045627120676,comdat
.Ltu_begin0:
...
.section .debug_names,"",@progbits
...
// DWARF32
.long .Ltu_begin0 # Type unit 0
// DWARF64
// .long .Ltu_begin0 # Type unit 0
```
When `.Ltu_begin0` is relative to a non-prevailing .debug_info section,
the relocation resolves to 0, which is a valid offset within the
.debug_info section.
```
cat > a.cc <<e
struct A { int x; };
inline A foo() { return {1}; }
int main() { foo(); }
e
cat > b.cc <<e
struct A { int x; };
inline A foo() { return {1}; }
void use() { foo(); }
e
clang++ -g -gpubnames -fdebug-types-section -fuse-ld=lld a.cc b.cc -o old
```
```
% llvm-dwarfdump old
...
Local Type Unit offsets [
LocalTU[0]: 0x00000000
]
...
Local Type Unit offsets [
LocalTU[0]: 0x00000000 // indistinguishable from a valid offset within .debug_info
]
```
https://dwarfstd.org/issues/231013.1.html proposes that we use a
tombstone value instead to inform consumers. This patch implements the
idea. The second LocalTU entry will now use 0xffffffff.
https://reviews.llvm.org/D84825 has a TODO that we should switch the
tombstone value for most `.debug_*` sections to UINT64_MAX. We have
postponed the change for more than three years for consumers to migrate.
At some point we shall make the change, so that .debug_names is no long
different from other debug section that is not .debug_loc/.debug_ranges.
Co-authored-by: Alexander Yermolovich <ayermolo@meta.com>
52 lines
1.9 KiB
ArmAsm
52 lines
1.9 KiB
ArmAsm
# REQUIRES: x86
|
|
## Test we resolve symbolic relocations in .debug_* sections to a tombstone
|
|
## value if the referenced symbol is discarded (--gc-sections, non-prevailing
|
|
## section group, SHF_EXCLUDE, /DISCARD/, etc).
|
|
|
|
# RUN: llvm-mc -filetype=obj -triple=i386 %s -o %t.o
|
|
# RUN: ld.lld %t.o -o %t
|
|
# RUN: llvm-objdump -s %t | FileCheck %s
|
|
|
|
# CHECK: Contents of section .debug_loc:
|
|
# CHECK-NEXT: 0000 01000000
|
|
# CHECK-NEXT: Contents of section .debug_ranges:
|
|
# CHECK-NEXT: 0000 01000000
|
|
# CHECK-NEXT: Contents of section .debug_addr:
|
|
# CHECK-NEXT: 0000 00000000
|
|
# CHECK-NEXT: Contents of section .debug_names:
|
|
# CHECK-NEXT: 0000 ffffffff
|
|
|
|
## -z dead-reloc-in-nonalloc= can override the tombstone value.
|
|
# RUN: ld.lld -z dead-reloc-in-nonalloc=.debug_loc=42 -z dead-reloc-in-nonalloc=.debug_addr=0xfffffffffffffffe %t.o -o %t1
|
|
# RUN: llvm-objdump -s %t1 | FileCheck %s --check-prefix=OVERRIDE
|
|
|
|
# OVERRIDE: Contents of section .debug_loc:
|
|
# OVERRIDE-NEXT: 0000 2a000000 *...
|
|
# OVERRIDE-NEXT: Contents of section .debug_ranges:
|
|
# OVERRIDE-NEXT: 0000 01000000 ....
|
|
# OVERRIDE-NEXT: Contents of section .debug_addr:
|
|
# OVERRIDE-NEXT: 0000 feffffff ....
|
|
|
|
.section .text.1,"axe"
|
|
.byte 0
|
|
|
|
## Resolved to UINT32_C(-2), with the addend ignored.
|
|
## UINT32_C(-1) is a reserved value (base address selection entry) which can't be used.
|
|
.section .debug_loc
|
|
.long .text.1+8
|
|
.section .debug_ranges
|
|
.long .text.1+16
|
|
|
|
## Resolved to UINT32_C(0), with the addend ignored.
|
|
.section .debug_addr
|
|
.long .text.1+8
|
|
|
|
.section .debug_info,"eG",@progbits,5657452045627120676,comdat
|
|
.Ltu_begin0:
|
|
|
|
.section .debug_names
|
|
## .debug_names may reference a local type unit defined in a COMDAT .debug_info
|
|
## section (-g -gpubnames -fdebug-types-section). If the referenced section is
|
|
## non-prevailing, resolve to UINT32_MAX.
|
|
.long .Ltu_begin0
|