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Fix building gio/tests/test_resources.o with LLVM ld

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Unlike GNU ld which has a default target architecture, ld.lld is always a
cross-linker and has the same behaviour for all targets. If you don't tell
ld.lld what the target architecture is it can't infer the right ELF flags
for the resulting object file.
```
$ ~/cheri/output/sdk/bin/ld -r -b binary gio/tests/test5.gresource -o gio/tests/test_resources.o -v
LLD 14.0.0 (compatible with GNU linkers)
ld: error: target emulation unknown: -m or at least one .o file required
```

As you can see from the error message it can't infer the target
architecture (you need a least one valid .o file or the -m flag).
If you use the compiler instead of directly invoking the linker it will
pass the appropriate flags:
```
$ ~/cheri/output/sdk/bin/clang -r -Wl,-b,binary gio/tests/test5.gresource -o gio/tests/test_resources.o -v
clang version 14.0.0 (https://github.com/CTSRD-CHERI/llvm-project.git ff66b683475fc44355b2010dbcbe1202d785e6f8)
Target: x86_64-unknown-linux-gnu
Thread model: posix
InstalledDir: /home/alexrichardson/cheri/output/sdk/bin
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/10
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/11
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/12
Selected GCC installation: /usr/lib/gcc/x86_64-linux-gnu/12
Candidate multilib: .;@m64
Selected multilib: .;@m64
 "/home/alexrichardson/cheri/output/sdk/bin/ld" --eh-frame-hdr -m elf_x86_64 -dynamic-linker /lib64/ld-linux-x86-64.so.2 -o gio/tests/test_resources.o -L/usr/lib/gcc/x86_64-linux-gnu/12 -L/usr/lib/gcc/x86_64-linux-gnu/12/../../../../lib64 -L/lib/x86_64-linux-gnu -L/lib/../lib64 -L/usr/lib/x86_64-linux-gnu -L/usr/lib/../lib64 -L/home/alexrichardson/cheri/output/sdk/bin/../lib -L/lib -L/usr/lib -r -b binary gio/tests/test5.gresource
❯ file gio/tests/test_resources.o
gio/tests/test_resources.o: ELF 64-bit LSB relocatable, x86-64, version 1 (SYSV), not stripped
```

This works for most architectures, but ones that need additional metadata
sections to encode the used ABI, etc. will require a different approach
using .incbin. However, that is a change for another MR.

Partially fixes: https://gitlab.gnome.org/GNOME/glib/-/issues/2720
This commit is contained in:
Alex Richardson 2023-01-08 11:14:35 +00:00
parent eafd19da29
commit 6d93568e36
1 changed files with 2 additions and 6 deletions
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8
gio/tests/meson.build
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@ -928,12 +928,8 @@ if not meson.is_cross_build()
test_resources_binary = custom_target('test_resources.o',
input : test_gresource_binary,
output : 'test_resources.o',
command : [ld,
'-z', 'noexecstack',
'-r',
'-b','binary',
'@INPUT@',
'-o','@OUTPUT@'])
command : cc.cmd_array() + ['-Wl,-z,noexecstack', '-r', '-Wl,-b,binary',
'@INPUT@', '-o','@OUTPUT@'])
# Rename symbol to match the one in the C file
if cc.get_id() == 'gcc' and host_system == 'windows'