Ignore -fPIC flag when not building relocatable code #9710
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This issue was supposed to have been fixed in lld but it seems that issues remain. See https://reviews.llvm.org/D65922. Fixes: #9690, #9013
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PTAL |
| def test_fpic_static(self): | ||
| self.emcc_args.append('-fPIC') | ||
| self.emcc_args.remove('-Werror') | ||
| self.do_run_in_out_file_test('tests', 'core', 'test_hello_world') |
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I don't think this is enough to hit the bug, at least not when i tested myself. I had to build tests/hello_libcxx.cpp which I guess includes enough libc++ to see breakage.
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This test fails withou the corresponding change to strip the -fPIC. I just reconfirmed. There might be multiple bugs but the emcc.py change makes this test start passing.
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Ah ok, sounds good on the test then.
| @@ -1883,6 +1883,9 @@ def is_link_flag(flag): | |||
| return any(flag.startswith(x) for x in ('-l', '-L', '-Wl,')) | |||
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| compile_args = [a for a in newargs if a and not is_link_flag(a)] | |||
| if '-fPIC' in compile_args and not shared.Settings.RELOCATABLE: | |||
| shared.warning('ignoring -fPIC flag when not building with SIDE_MODULE or MAIN_MODULE') | |||
| compile_args.remove('-fPIC') | |||
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You explained this to me but I realize I still don't get it, sorry. What happens in this case:
emcc a.c -fPIC -c
emcc a.o -s SIDE_MODULE
It seems like the first command will lose the -fPIC, so it will try to link a non-PIC into a SIDE_MODULE. I think you said that errors? Would the only way to avoid the error be to pass SIDE_MODULE at compile time too?
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Yes and yes.
For now, until we fix the underlying issue with static linking of PIC objects, then we can allow -fPIC to control this again.
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Sgtm, but (separately from this PR if you want) please update the docs to mention that with the new backend, MAIN/SIDE_MODULES must have their source files built with MAIN/SIDE_MODULE. E.g. here in the list of big backend differences, https://emscripten.org/docs/compiling/WebAssembly.html#backends
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Please add this to the docs (that with the new backend, one must add flags a compile time too). And also this is a breaking change for some users (as |
…#9710) This issue was supposed to have been fixed in lld but it seems that issues remain. See https://reviews.llvm.org/D65922. Fixes: emscripten-core#9690, emscripten-core#9013
This issue was supposed to have been fixed in lld but it seems that
issues remain. See https://reviews.llvm.org/D65922.
Fixes: #9690, #9013