Enable real dynamic linking with `-shared` by default by sbc100 · Pull Request #25930 · emscripten-core/emscripten

sbc100 · 2025-12-11T00:38:48Z

This change essentially disables FAKE_DYLIBS by default, which in
turn means -shared will now produce dynamic libraries by default.

If you want the old behaviour you now need -sFAKE_DYLIBS.

dschuff

I wonder what would happen if we tested this with Binaryen. it doesn't seem prepared to force the Emscripten build to be static (assuming that's the behavior we actually want).

This test was first added in c735bb6. Hopefully these changes make it more obvious what is being tested, and also test more commonly used flags (`-shared` vs `-r`). Split out from #25930.

sbc100 · 2026-05-15T19:18:57Z

I wonder what would happen if we tested this with Binaryen. it doesn't seem prepared to force the Emscripten build to be static (assuming that's the behavior we actually want).

I actually ended up leaving the cmake TARGET_SUPPORTS_SHARED_LIBS setting as False until we resolve https://gitlab.kitware.com/cmake/cmake/-/work_items/27240

sbc100 · 2026-05-15T19:20:07Z

OK, I think this change is in pretty good shape now

sbc100 · 2026-05-16T00:48:40Z

@kripken @dschuff this change is pretty small now. No codesize changes anymore.

sbc100 · 2026-05-20T20:59:51Z

OK, cmake issue is now resolved I believe.

kripken · 2026-05-20T23:31:08Z

+    self.run_process([EMCC, 'libdir/libfile.c', '-sFAKE_DYLIBS', '-shared', '-fPIC', '-o', 'libdir/libfile.so' + lib_suffix])
    # Build libother and dynamically link it to libfile
-    self.run_process([EMCC, '-Llibdir', 'libdir/libother.c'] + link_flags + ['-shared', '-o', 'libdir/libother.so'])
+    self.run_process([EMCC, '-Llibdir', 'libdir/libother.c'] + link_flags + ['-sFAKE_DYLIBS', '-shared', '-fPIC', '-o', 'libdir/libother.so'])


Here I think we do need a comment on the new flag? I don't see one in this function.

I split out a change to remove this redundant test: #26986

This change essentially disables `FAKE_DYLIBS` by default, which in turn means `-shared` will now produce dynamic libraries by default. If you want the old behaviour you now need `-sFAKE_DYLIBS`.

kripken

lgtm % comment

sbc100 force-pushed the shared_flag_part2 branch from 655b473 to e01726b Compare December 11, 2025 00:39

sbc100 commented Dec 11, 2025

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sbc100 force-pushed the shared_flag_part2 branch from 3b0addc to 2a98976 Compare May 12, 2026 01:15

sbc100 changed the title ~~Disable FAKE_DYLIBS by default~~ Enable real dynamic linking by default May 12, 2026

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sbc100 mentioned this pull request May 14, 2026

Improve test_multiply_defined_libsymbols #26953

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sbc100 changed the title ~~Enable real dynamic linking by default~~ Enable real dynamic linking with -shared by default May 15, 2026

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sbc100 added 3 commits May 21, 2026 09:47

Enable real dynamic linking with -shared by default

f7f4ca4

This change essentially disables `FAKE_DYLIBS` by default, which in turn means `-shared` will now produce dynamic libraries by default. If you want the old behaviour you now need `-sFAKE_DYLIBS`.

feedback

f28581f

Merge remote-tracking branch 'upstream/main' into shared_flag_part2

517da81

sbc100 force-pushed the shared_flag_part2 branch from 432394d to 517da81 Compare May 21, 2026 18:14

kripken reviewed May 21, 2026

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sbc100 added 3 commits May 21, 2026 11:40

feedback

9dfed2e

fix tests

b305b6d

Merge remote-tracking branch 'upstream/main' into shared_flag_part2

0947279

sbc100 disabled auto-merge May 21, 2026 22:04

sbc100 merged commit bbc19e2 into emscripten-core:main May 21, 2026
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sbc100 deleted the shared_flag_part2 branch May 21, 2026 22:04

neondev9 mentioned this pull request May 29, 2026

CMake Toolkit: Shared Library as Side Module #16281

Closed

enetheru mentioned this pull request May 30, 2026

CMAKE: Emscripten shared lib hack is now resolved upstream godotengine/godot-cpp#1993

Open

sbc100 mentioned this pull request Jun 1, 2026

bazel build seems to have having trouble with the trasition to true shared libraries. emscripten-core/emsdk#1714

Open

sbc100 mentioned this pull request Jun 11, 2026

emsdk 6.0.0 and dynamic linking... #27104

Open

hoodmane mentioned this pull request Jul 22, 2026

Trouble with emcc 6.0.0 from #25930 #27403

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hoodmane added a commit to pyodide/pyodide that referenced this pull request Jul 28, 2026

Reduce patch to fix emscripten-core/emscripten#25930 regression (#6387)

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hoodmane mentioned this pull request Jul 28, 2026

Make sure -sSIDE_MODULE=1 passes --whole-archive to linker #27430

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hoodmane added a commit to pyodide/pyodide that referenced this pull request Jul 28, 2026

Reduce patch to fix emscripten-core/emscripten#25930 regression (#6387)

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hoodmane added a commit to pyodide/pyodide that referenced this pull request Jul 29, 2026

Reduce patch to fix emscripten-core/emscripten#25930 regression (#6387)

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sbc100 commented Dec 11, 2025 •

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