https://sourceware.org/bugzilla/show_bug.cgi?id=33191
Bug ID: 33191
Summary: RISC-V relaxation affects unrelated symbol
Product: binutils
Version: unspecified
Status: UNCONFIRMED
Severity: normal
Priority: P2
Component: ld
Assignee: unassigned at sourceware dot org
Reporter: luismarques at lowrisc dot org
Target Milestone: ---
For context, this bug is the binutils/ld counterpart of essentially the same
LLD bug we filed earlier: https://github.com/llvm/llvm-project/issues/149583
In the following reproducer, the symbol x is being moved due to the call
relaxation, when it arguably shouldn't be affected, as it's defined only
relative to _start.
$ cat bug.s
.text
.global _start
_start:
call _start
.equ x, _start + 8
$ riscv64-linux-gnu-gcc -march=rv32i -mabi=ilp32 -mrelax -nostdlib -o bug bug.s
&& readelf -Ws bug
Symbol table '.symtab' contains 25 entries:
Num: Value Size Type Bind Vis Ndx Name
0: 00000000 0 NOTYPE LOCAL DEFAULT UND
(...)
12: 000001bc 0 NOTYPE LOCAL DEFAULT 6 x
(...)
19: 000001b8 0 NOTYPE GLOBAL DEFAULT 6 _start
That is, we observe x = _start + 4 instead of _start + 8.
For completeness, we have the following combinations of `x = _start + offset`
requested offsets and generated offsets:
| offset | LLD | Binutils |
|--------|--------|----------|
| -1 | -1 - 4 | -1 |
| 0 | 0 | 0 |
| 1 | 1 - 4 | 1 |
| 4 | 4 - 4 | 4 |
| 5 | 5 - 4 | 5 - 4 |
| 8 | 8 - 4 | 8 - 4 |
| 9 | 9 - 4 | 9 |
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