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Strip -fPIC compiler flag during compilation #10209

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Merged
merged 1 commit into from
Jan 15, 2020
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Strip -fPIC compiler flag during compilation #10209

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3 changes: 3 additions & 0 deletions emcc.py
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Original file line number Diff line number Diff line change
Expand Up @@ -1937,6 +1937,9 @@ def is_link_flag(flag):
return any(flag.startswith(x) for x in ('-l', '-L', '-Wl,'))

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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This change means that people need to compile with SIDE/MAIN_MODULE and not just link? Is that new or am I forgetting how upstream worked here?

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Yes, I think that is true. But they will see this warning so it should be clear.

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I think this is pretty good intermediate fix until the binaryen fix is ready.

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Sounds good.

How do our current tests pass, then? It seems like all dylink/dlfcn tests should warn if they include more than 1 file, since I don't see this flag added to their compile commands?

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Agreed it's good to have a temp fix. I'm just trying to fully understand it.

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But none of our dylink currently pass -fPIC. So this means they must all be passing SIDE/MAIN_MODULE during both compile and link.

As far as I know we never advertised the fact that -fPIC could be used at compile time instead of SIDE/MAIN_MODULE.

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Interesting, good point.

We should probably add more realistic tests then, if users are using -fPIC for dynamic linking but our tests aren't.

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IIUC users are not using fPIC for dyamic linking, they are using it simply because their build system always adds it in, but they are doing static linking.


# Bitcode args generation code
def get_clang_command(input_files):
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1 change: 1 addition & 0 deletions tests/test_core.py
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Expand Up @@ -8554,6 +8554,7 @@ def test_undefined_main(self):

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')

@node_pthreads
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