Add Emscripten compat include paths to wasm kernel specs #409

anutosh491 · 2025-11-11T08:26:29Z

Description

Discovered this while moving to emscripten 4-x for xeus-cpp.

Problem : The following works for our native kernel but not our wasm kernel

native

2) wasm

Type of change

Please tick all options which are relevant.

Bug fix
New feature
Added/removed dependencies
Required documentation updates

anutosh491 · 2025-11-11T08:26:56Z

What's Happening here ?

So on native builds, clang automatically discovers <xlocale.h> through the system SDK or libc include paths.
In the Emscripten sysroot, however, legacy headers like <xlocale.h> reside under /include/compat, which isn’t part of the default search list.

How emcc does it

anutosh491@Anutoshs-MacBook-Air xeus-cpp % cat xlocale_test.c
#include <stdio.h>
#include <locale.h>
#include <xlocale.h>

int main(void) {
    locale_t loc = newlocale(LC_NUMERIC_MASK, "C", NULL);

    const char *s = "3.14159";
    long double v = strtold_l(s, NULL, loc);

    printf("Parsed value: %.5Lf\n", v);

    freelocale(loc);
    return 0;
}

anutosh491@Anutoshs-MacBook-Air xeus-cpp % emcc -v xlocale_test.c -o xlocale_test.html
 /Users/anutosh491/work/emsdk/upstream/bin/clang -target wasm32-unknown-emscripten -fignore-exceptions -mllvm -combiner-global-alias-analysis=false -mllvm -enable-emscripten-sjlj -mllvm -disable-lsr --sysroot=/Users/anutosh491/work/emsdk/upstream/emscripten/cache/sysroot -DEMSCRIPTEN -Xclang -iwithsysroot/include/fakesdl -Xclang -iwithsysroot/include/compat -v -c xlocale_test.c -o /var/folders/m1/cdn74f917994jd99d_2cpf440000gn/T/emscripten_temp_v4f2uvqa/xlocale_test.o
clang version 22.0.0git (https:/github.com/llvm/llvm-project c13ac9cadf1f9b4fa886b82d1e84a5feb0439023)
Target: wasm32-unknown-emscripten
Thread model: posix
InstalledDir: /Users/anutosh491/work/emsdk/upstream/bin
 (in-process)
 "/Users/anutosh491/work/emsdk/upstream/bin/clang-22" -cc1 -triple wasm32-unknown-emscripten -emit-obj -disable-free -clear-ast-before-backend -disable-llvm-verifier -discard-value-names -main-file-name xlocale_test.c -mrelocation-model static -mframe-pointer=none -ffp-contract=on -fno-rounding-math -mconstructor-aliases -target-cpu generic -fvisibility=hidden -debugger-tuning=gdb -fdebug-compilation-dir=/Users/anutosh491/work/xeus-cpp -v -fcoverage-compilation-dir=/Users/anutosh491/work/xeus-cpp -resource-dir /Users/anutosh491/work/emsdk/upstream/lib/clang/22 -D EMSCRIPTEN -isysroot /Users/anutosh491/work/emsdk/upstream/emscripten/cache/sysroot -internal-isystem /Users/anutosh491/work/emsdk/upstream/lib/clang/22/include -internal-isystem /Users/anutosh491/work/emsdk/upstream/emscripten/cache/sysroot/include/wasm32-emscripten -internal-isystem /Users/anutosh491/work/emsdk/upstream/emscripten/cache/sysroot/include -ferror-limit 19 -fmessage-length=141 -fgnuc-version=4.2.1 -fskip-odr-check-in-gmf -fignore-exceptions -fcolor-diagnostics -iwithsysroot/include/fakesdl -iwithsysroot/include/compat -mllvm -combiner-global-alias-analysis=false -mllvm -enable-emscripten-sjlj -mllvm -disable-lsr -o /var/folders/m1/cdn74f917994jd99d_2cpf440000gn/T/emscripten_temp_v4f2uvqa/xlocale_test.o -x c xlocale_test.c
clang -cc1 version 22.0.0git based upon LLVM 22.0.0git default target 
ignoring nonexistent directory "/Users/anutosh491/work/emsdk/upstream/emscripten/cache/sysroot/include/wasm32-emscripten"
#include "..." search starts here:
#include <...> search starts here:
 /Users/anutosh491/work/emsdk/upstream/emscripten/cache/sysroot/include/compat
 /Users/anutosh491/work/emsdk/upstream/lib/clang/22/include
 /Users/anutosh491/work/emsdk/upstream/emscripten/cache/sysroot/include
End of search list.

This shows 3 paths
i) sysroot/include and lib/clang/22/include (resource dir) which we address as of now
ii) What we don't address is sysroot/include/compat !!!!

As can be seen this is addressed through -iwithsysroot/include/compat as can be seen above and here

This PR adds the same (check right side of the img below as now we're able to search through compat for xlocale.h)

codecov-commenter · 2025-11-11T08:29:45Z

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 81.94%. Comparing base (659e968) to head (6eb1b70).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #409      +/-   ##
==========================================
- Coverage   82.05%   81.94%   -0.11%     
==========================================
  Files          21       21              
  Lines         858      853       -5     
  Branches       89       87       -2     
==========================================
- Hits          704      699       -5     
  Misses        154      154

🚀 New features to boost your workflow:

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anutosh491 · 2025-11-11T08:30:08Z

cc @mcbarton

The same change would be needed in cppinterop to run the emscripten tests (cause iostream and other stream based headers from emsdk 4-x started including xlocale.h) once we migrate.

Otherwise some tests would just fail through

1: [ RUN      ] CppInterOpTest/InProcessJIT.ScopeReflectionTestIsBuiltin
1: In file included from <<< inputs >>>:1:
1: In file included from input_line_2:1:
1: In file included from /include/c++/v1/complex:273:
1: In file included from /include/c++/v1/sstream:323:
1: In file included from /include/c++/v1/__ostream/basic_ostream.h:20:
1: In file included from /include/c++/v1/__ostream/put_character_sequence.h:19:
1: In file included from /include/c++/v1/__locale_dir/pad_and_output.h:16:
1: In file included from /include/c++/v1/ios:223:
1: In file included from /include/c++/v1/__locale:17:
1: /include/c++/v1/__locale_dir/locale_base_api.h:131:16: fatal error: 'xlocale.h' file not found
1:   131 | #      include <xlocale.h>
1:       |                ^~~~~~~~~~~
1: wasm://wasm/13cfc366:1

I just ran the cppinterop tests (after building both cppinterop and llvm against latest emsdk 4-x) and this is where I caught the above.

github-actions · 2025-11-11T08:33:17Z

clang-tidy review says "All clean, LGTM! 👍"

mcbarton · 2025-11-11T08:35:08Z

cc @mcbarton

The same change would be needed in cppinterop to run the emscripten tests (cause iostream from emsdk 4-x started including xlocale.h) once we migrate.

Otherwise some tests would just fail through

1: [ RUN      ] CppInterOpTest/InProcessJIT.ScopeReflectionTestIsBuiltin
1: In file included from <<< inputs >>>:1:
1: In file included from input_line_2:1:
1: In file included from /include/c++/v1/complex:273:
1: In file included from /include/c++/v1/sstream:323:
1: In file included from /include/c++/v1/__ostream/basic_ostream.h:20:
1: In file included from /include/c++/v1/__ostream/put_character_sequence.h:19:
1: In file included from /include/c++/v1/__locale_dir/pad_and_output.h:16:
1: In file included from /include/c++/v1/ios:223:
1: In file included from /include/c++/v1/__locale:17:
1: /include/c++/v1/__locale_dir/locale_base_api.h:131:16: fatal error: 'xlocale.h' file not found
1:   131 | #      include <xlocale.h>
1:       |                ^~~~~~~~~~~
1: wasm://wasm/13cfc366:1

I just ran the cppinterop tests (after building both cppinterop and llvm against latest emsdk 4-x) and this is where I caught the above.

Thanks the tip @anutosh491 . I will look into this. Did you run the llvm Emscripten tests to see if a change is needed to get them to still pass too?

anutosh491 · 2025-11-11T08:39:23Z

Did you run the llvm Emscripten tests to see if a change is needed to get them to still pass too?

Not yet !

But we probably won't need any change there as this is the only real change I could spot. The llvm emscripten tests don't really process any "#Include" 's as such which means no include path searching change !

test/test_interpreter.cpp

github-actions · 2025-11-11T08:54:29Z

clang-tidy review says "All clean, LGTM! 👍"

github-actions · 2025-11-11T09:11:04Z

clang-tidy review says "All clean, LGTM! 👍"

src/xinterpreter.cpp

github-actions · 2025-11-13T06:27:45Z

clang-tidy review says "All clean, LGTM! 👍"

github-actions · 2025-11-13T06:41:09Z

clang-tidy review says "All clean, LGTM! 👍"

github-actions · 2025-11-13T06:45:51Z

clang-tidy review says "All clean, LGTM! 👍"

vgvassilev

LGTM!

Add supporting tests

github-actions · 2025-11-18T15:30:47Z

clang-tidy review says "All clean, LGTM! 👍"

anutosh491 · 2025-11-20T17:10:58Z

Hi,

Thanks for the approval here.

This is very much needed cause I was able to build xeus-cpp on emscripten-forge's emscripten 4-x branch and got this.

Because all the stream based headers (iostream, sstream, fstream etc) defined in emsdk's 4-x sysroot started including xlocale.h. And without this fix, we would have the above error.

github-actions · 2025-11-20T17:17:10Z

clang-tidy review says "All clean, LGTM! 👍"

anutosh491 commented Nov 11, 2025

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test/test_interpreter.cpp Outdated Show resolved Hide resolved

anutosh491 requested review from JohanMabille, mcbarton and vgvassilev November 11, 2025 09:28

vgvassilev reviewed Nov 11, 2025

View reviewed changes

src/xinterpreter.cpp Outdated Show resolved Hide resolved

anutosh491 force-pushed the compat branch from 377035f to 25b61b9 Compare November 13, 2025 06:21

anutosh491 changed the title ~~Add Emscripten compat include paths to interpreter initialization~~ Add Emscripten compat include paths to wasm kernel specs Nov 13, 2025

vgvassilev approved these changes Nov 18, 2025

View reviewed changes

anutosh491 added 3 commits November 18, 2025 16:25

Add Emscripten compat include paths to wasm kernel specs.

361dea2

Add supporting tests

fix test

9a162bb

remove whitespace in xinterpreter.cpp

e2fa913

vgvassilev force-pushed the compat branch from b3a25f5 to e2fa913 Compare November 18, 2025 15:25

Merge branch 'main' into compat

6eb1b70

anutosh491 merged commit 62268e7 into compiler-research:main Nov 20, 2025
17 of 18 checks passed

anutosh491 deleted the compat branch November 20, 2025 17:20

Add Emscripten compat include paths to wasm kernel specs #409

Add Emscripten compat include paths to wasm kernel specs #409

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anutosh491 commented Nov 11, 2025

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