[PATCH] D100651: [AIX] Support of Big archive (read)

[Guesnet via Phabricator via llvm-commits]

EGuesnet added inline comments.


================
Comment at: llvm/lib/Object/Archive.cpp:1013
+    return child_end();
+  const char *Loc = Data.getBufferStart() + strlen(Magic) + sizeof(Archive::ArFixLenHdrType);
+  Child C(this, Loc, &Err);
----------------
Esme wrote:
> It's not correct to calculate the offset of the first archive member by `Data.getBufferStart() + strlen(Magic) + sizeof(Archive::ArFixLenHdrType);`, please use the value of  `ArFixLenHdr->FirstArOffset`.
> You can easily reproduce the bug if you test a archive file which contains a object file member like the comment I added before:
> ```
> $ xlc 1.c -o 1.o
> $ ar -v -q 1.a 1.o
> $ llvm-ar tv 1.a
> llvm-ar: error: unable to load '1.a': truncated or malformed archive (characters in size field in archive header are not all decimal numbers: '\000\000\000\000\000\000\000\000\000\0005892' for archive member header at offset 128)
> ``` 
> The correct offset for this case should be 138 instead of 128.
First, LLVM is no more a priority of our team, so I cannot spend time to this PR.
Second, I am not able to reproduce. Please give me content of 1.c, and content of 1.a.
```
// small.c
int add_two (int a) {
        return a + 2;
}

$ xlc -v
C for AIX Compiler, Version 5

OK, really old, but we don't care for archive.

$ xlc small.c  -o small.o -c
$ ar -v -q small.a small.o

$ xxd small.a

00000000: 3c62 6967 6166 3e0a 3130 3730 2020 2020  <bigaf>.1070
00000010: 2020 2020 2020 2020 2020 2020 3132 3332              1232
00000020: 2020 2020 2020 2020 2020 2020 2020 2020
00000030: 3020 2020 2020 2020 2020 2020 2020 2020  0
00000040: 2020 2020 3132 3820 2020 2020 2020 2020      128
00000050: 2020 2020 2020 2020 3132 3820 2020 2020          128
00000060: 2020 2020 2020 2020 2020 2020 3020 2020              0
00000070: 2020 2020 2020 2020 2020 2020 2020 2020
// End of Fixed-Length Header: size is 128
00000080: 3832 3020 2020 2020 2020 2020 2020 2020  820
00000090: 2020 2020 3130 3730 2020 2020 2020 2020      1070
000000a0: 2020 2020 2020 2020 3020 2020 2020 2020          0
000000b0: 2020 2020 2020 2020 2020 2020 3136 3331              1631
000000c0: 3630 3435 3039 2020 3020 2020 2020 2020  604509  0
000000d0: 2020 2020 3020 2020 2020 2020 2020 2020      0
000000e0: 3634 3420 2020 2020 2020 2020 3720 2020  644         7
[...]

$ llvm-ar --version
LLVM version 13.0.0

$ llvm-ar t small.a
small.o # OK
```

Third, according documentation https://www.ibm.com/docs/en/aix/7.2?topic=formats-ar-file-format-big , Fixed-Length Header must have a size of 128. 138 is not valide.


Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D100651/new/

https://reviews.llvm.org/D100651