https://gcc.gnu.org/bugzilla/show_bug.cgi?id=78529
Renlin Li <renlin at gcc dot gnu.org> changed:
What |Removed |Added
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CC| |renlin at gcc dot gnu.org
--- Comment #22 from Renlin Li <renlin at gcc dot gnu.org> ---
(In reply to James Greenhalgh from comment #19)
> That would be an error:
>
> /tmp/ccpefK3l.ltrans0.ltrans.o: In function `memset':
> <artificial>:(.text+0x4a0): multiple definition of `memset'
> .../aarch64-none-elf/lib/libc.a(lib_a-memset.o):
> .../newlib/libc/machine/aarch64/memset.S:90: first defined here
>
> Were it not for the flag added to resolve PR55994
> -Wl,--allow-multiple-definition .
>
> So, in my opinion, the testcase is broken and could always have failed in
> this way. The combination of register allocation, LTO and order the linker
> sees symbols explains why this is hard to reproduce.
I had exactly the same errors and issues today.
I reduced it to a minimum test case. Please check the new attachment
The build command line is:
aarch64-none-elf-gcc -O2 -specs=aem-ve.specs -Wl,--allow-multiple-definition
-lm -flto main.c memset.c -o new.exe
The expected output should be "A A A 2"
0000000080001038 <main>:
80001038: a9bf7bfd stp x29, x30, [sp,#-16]!
8000103c: 90000123 adrp x3, 80025000 <__global_locale+0x68>
80001040: 52800044 mov w4, #0x2 // #2
80001044: 91060060 add x0, x3, #0x180
80001048: 910003fd mov x29, sp
8000104c: b9018064 str w4, [x3,#384]
80001050: d2800402 mov x2, #0x20 // #32
80001054: 52800821 mov w1, #0x41 // #65
80001058: 91002000 add x0, x0, #0x8
# At this function entry, x4 is not saved. Because LTO thinks the local memset
# implementation will not clobber it. However, the libc version of memeset is
# linked in the final binary. The implementation there will clobber x4. This
# will cause run-time data corruption, which is shown here.
8000105c: 94000a39 bl 80003940 <memset>
80001060: a8c17bfd ldp x29, x30, [sp],#16
80001064: 52800823 mov w3, #0x41 // #65
80001068: 90000080 adrp x0, 80011000 <__swbuf_r+0x70>
8000106c: 2a0303e2 mov w2, w3
80001070: 2a0303e1 mov w1, w3
80001074: 91152000 add x0, x0, #0x548
80001078: 140015c0 b 80006778 <printf>
8000107c: 00000000 .inst 0x00000000 ; undefined
This is mentioned above. But allow me to ask again:
"aarch64-none-elf-gcc -O2 main.c memset.c -o new.o -specs=aem-ve.specs -lm
-flto"
will give the "multiple definition of `memset'" error
while
"aarch64-none-elf-gcc -O2 main.c memset.c -o new.o -specs=aem-ve.specs -lm"
won't.
Should them behavior the same? By adding "-Wl,--allow-multiple-definition" do
fix this erro. But why it's the test case that is broken instead of the lto
pass?
