Repository: rust
Issue: [wasm32-unknown-emscripten] undefined symbols: longjmp, setjmp
Labels: O-wasm,C-bug,O-emscripten

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When the target is wasm32-unknown-emscripten, unable to find symbols: longjmp, setjmp, setjmp-longjmp support is enabled by default in Emscripten.
https://emscripten.org/docs/porting/setjmp-longjmp.html



I tried this code:

```rust
use ::libc;
extern "C" {
    fn printf(_: *const libc::c_char, _: ...) -> libc::c_int;
    fn setjmp(_: *mut libc::c_void) -> libc::c_int;
    fn longjmp(_: *mut libc::c_void, _: libc::c_int) -> !;
}


pub static mut exception_buffer: [u8; 100] = [0u8; 100];

pub unsafe extern "C" fn do_something(value: libc::c_int) {
    if value < 0 as libc::c_int {
        printf(
            b"do_something: Error! Value cannot be negative.\n\0" as *const u8
                as *const libc::c_char,
        );
        longjmp(
            exception_buffer.as_mut_ptr() as *mut libc::c_void,
            1 as libc::c_int,
        );
    }
    printf(
        b"do_something: Value is %d\n\0" as *const u8 as *const libc::c_char,
        value,
    );
}
fn main() {
    unsafe {
        let value: libc::c_int = -(5 as libc::c_int);
        if setjmp(exception_buffer.as_mut_ptr() as *mut libc::c_void) == 0 as libc::c_int {
            printf(
                b"Main: Setting up exception handling...\n\0" as *const u8 as *const libc::c_char,
            );
            do_something(value);
        } else {
            printf(b"Main: Handling exception...\n\0" as *const u8 as *const libc::c_char);
        }
        printf(
            b"Main: Program continues after exception handling.\n\0" as *const u8
                as *const libc::c_char,
        );
    }
}
```

I expected to see this happen: *explanation*
`cargo run`
```
Main: Setting up exception handling...
do_something: Error! Value cannot be negative.
Main: Handling exception...
Main: Program continues after exception handling.
```
Instead, this happened: *explanation*
`cargo run --target=wasm32-unknown-emscripten`

```
  = note: wasm-ld: error: /root/ct/wasm32-unknown-emscripten/debug/deps/emsdk_demo.5eeji6ymekqs85b7.rcgu.o: undefined symbol: longjmp
          wasm-ld: error: /root/ct/wasm32-unknown-emscripten/debug/deps/emsdk_demo.5eeji6ymekqs85b7.rcgu.o: undefined symbol: setjmp

```

### Meta
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If you're using the stable version of the compiler, you should also check if the
bug also exists in the beta or nightly versions.
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`rustc --version --verbose`:
```
rustc 1.76.0-nightly (2b603f95a 2023-11-12)
binary: rustc
commit-hash: 2b603f95a48f10f931a61dd208fe3e5ffd64e491
commit-date: 2023-11-12
host: x86_64-unknown-linux-gnu
release: 1.76.0-nightly
LLVM version: 17.0.4


rustc 1.74.0 (79e9716c9 2023-11-13)
binary: rustc
commit-hash: 79e9716c980570bfd1f666e3b16ac583f0168962
commit-date: 2023-11-13
host: x86_64-unknown-linux-gnu
release: 1.74.0
LLVM version: 17.0.4
```

<!--
Include a backtrace in the code block by setting `RUST_BACKTRACE=1` in your
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<details><summary>Backtrace</summary>
<p>

```
RUST_BACKTRACE=1 cargo build --target=wasm32-unknown-emscripten#                                                                                                            
u23#  RUST_BACKTRACE=1 cargo build --target=wasm32-unknown-emscripten
   Compiling emsdk-demo v0.1.0 (/root/code/emsdk-demo)
warning: static variable `exception_buffer` should have an upper case name
 --> src/main.rs:9:16
  |
9 | pub static mut exception_buffer: [u8; 100] = [0u8; 100];
  |                ^^^^^^^^^^^^^^^^ help: convert the identifier to upper case: `EXCEPTION_BUFFER`
  |
  = note: `#[warn(non_upper_case_globals)]` on by default

error: linking with `emcc` failed: exit status: 1
  |
  = note: LC_ALL="C" PATH="/root/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/x86_64-unknown-linux-gnu/bin:/root/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/x86_64-unknown-linux-gnu/bin/self-contained:/root/code/emsdk:/root/code/emsdk/upstream/emscripten:/run/user/0/fnm_multishells/51368_1701605570612/bin:/root/.vscode-server/bin/1a5daa3a0231a0fbba4f14db7ec463cf99d7768e/bin/remote-cli:/root/.local/share/pnpm:/root/.cargo/bin:/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/usr/games:/usr/local/games:/snap/bin" VSLANG="1033" "emcc" "-s" "EXPORTED_FUNCTIONS=[\"_main\"]" "/root/ct/wasm32-unknown-emscripten/debug/deps/emsdk_demo.1wof4idzl24j4p0a.rcgu.o" "/root/ct/wasm32-unknown-emscripten/debug/deps/emsdk_demo.2nt1liv8b0dfeizm.rcgu.o" "/root/ct/wasm32-unknown-emscripten/debug/deps/emsdk_demo.43djbu2r1eeqpn12.rcgu.o" "/root/ct/wasm32-unknown-emscripten/debug/deps/emsdk_demo.5eeji6ymekqs85b7.rcgu.o" "/root/ct/wasm32-unknown-emscripten/debug/deps/emsdk_demo.vg9f46yl3mh9xiu.rcgu.o" "/root/ct/wasm32-unknown-emscripten/debug/deps/emsdk_demo.2t7mycb9l7k0tgy.rcgu.o" "-L" "/root/ct/wasm32-unknown-emscripten/debug/deps" "-L" "/root/ct/debug/deps" "-L" "/root/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/wasm32-unknown-emscripten/lib" "/root/ct/wasm32-unknown-emscripten/debug/deps/liblibc-9bc98c84e1a910dc.rlib" "/root/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/wasm32-unknown-emscripten/lib/libstd-61e93cdfb239f7c2.rlib" "/root/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/wasm32-unknown-emscripten/lib/libpanic_unwind-c51bd600d3569b2d.rlib" "/root/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/wasm32-unknown-emscripten/lib/librustc_demangle-8e67090878f28f69.rlib" "/root/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/wasm32-unknown-emscripten/lib/libstd_detect-3fb9a4c301477b79.rlib" "/root/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/wasm32-unknown-emscripten/lib/libhashbrown-5c1b3f61e45e4bf0.rlib" "/root/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/wasm32-unknown-emscripten/lib/librustc_std_workspace_alloc-f99cb7d3c28bae00.rlib" "/root/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/wasm32-unknown-emscripten/lib/libminiz_oxide-942831f28a82cd36.rlib" "/root/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/wasm32-unknown-emscripten/lib/libadler-8e620a0166013244.rlib" "/root/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/wasm32-unknown-emscripten/lib/libunwind-b17b8f660cd36185.rlib" "/root/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/wasm32-unknown-emscripten/lib/libcfg_if-0c7bacfbf87cda18.rlib" "/root/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/wasm32-unknown-emscripten/lib/liblibc-48b2b822b890a628.rlib" "/root/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/wasm32-unknown-emscripten/lib/liballoc-e119f963323764f2.rlib" "/root/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/wasm32-unknown-emscripten/lib/librustc_std_workspace_core-dccfe230458f39f9.rlib" "/root/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/wasm32-unknown-emscripten/lib/libcore-ff850c1994b8a1ec.rlib" "/root/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/wasm32-unknown-emscripten/lib/libcompiler_builtins-295fcaa60ab90f2f.rlib" "-l" "c" "-B/root/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/x86_64-unknown-linux-gnu/bin/gcc-ld" "-fuse-ld=lld" "--target=wasm32-unknown-emscripten" "-s" "DISABLE_EXCEPTION_CATCHING=0" "-L" "/root/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/wasm32-unknown-emscripten/lib" "-L" "/root/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/wasm32-unknown-emscripten/lib/self-contained" "-o" "/root/ct/wasm32-unknown-emscripten/debug/deps/emsdk_demo.js" "-O0" "-g" "-sABORTING_MALLOC=0" "-Wl,--fatal-warnings"
  = note: wasm-ld: error: /root/ct/wasm32-unknown-emscripten/debug/deps/emsdk_demo.5eeji6ymekqs85b7.rcgu.o: undefined symbol: longjmp
          wasm-ld: error: /root/ct/wasm32-unknown-emscripten/debug/deps/emsdk_demo.5eeji6ymekqs85b7.rcgu.o: undefined symbol: setjmp
          emcc: error: '/root/code/emsdk/upstream/bin/wasm-ld -o /root/ct/wasm32-unknown-emscripten/debug/deps/emsdk_demo.wasm /root/ct/wasm32-unknown-emscripten/debug/deps/emsdk_demo.1wof4idzl24j4p0a.rcgu.o /root/ct/wasm32-unknown-emscripten/debug/deps/emsdk_demo.2nt1liv8b0dfeizm.rcgu.o /root/ct/wasm32-unknown-emscripten/debug/deps/emsdk_demo.43djbu2r1eeqpn12.rcgu.o /root/ct/wasm32-unknown-emscripten/debug/deps/emsdk_demo.5eeji6ymekqs85b7.rcgu.o /root/ct/wasm32-unknown-emscripten/debug/deps/emsdk_demo.vg9f46yl3mh9xiu.rcgu.o /root/ct/wasm32-unknown-emscripten/debug/deps/emsdk_demo.2t7mycb9l7k0tgy.rcgu.o -L/root/ct/wasm32-unknown-emscripten/debug/deps -L/root/ct/debug/deps -L/root/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/wasm32-unknown-emscripten/lib /root/ct/wasm32-unknown-emscripten/debug/deps/liblibc-9bc98c84e1a910dc.rlib /root/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/wasm32-unknown-emscripten/lib/libstd-61e93cdfb239f7c2.rlib /root/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/wasm32-unknown-emscripten/lib/libpanic_unwind-c51bd600d3569b2d.rlib /root/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/wasm32-unknown-emscripten/lib/librustc_demangle-8e67090878f28f69.rlib /root/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/wasm32-unknown-emscripten/lib/libstd_detect-3fb9a4c301477b79.rlib /root/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/wasm32-unknown-emscripten/lib/libhashbrown-5c1b3f61e45e4bf0.rlib /root/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/wasm32-unknown-emscripten/lib/librustc_std_workspace_alloc-f99cb7d3c28bae00.rlib /root/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/wasm32-unknown-emscripten/lib/libminiz_oxide-942831f28a82cd36.rlib /root/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/wasm32-unknown-emscripten/lib/libadler-8e620a0166013244.rlib /root/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/wasm32-unknown-emscripten/lib/libunwind-b17b8f660cd36185.rlib /root/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/wasm32-unknown-emscripten/lib/libcfg_if-0c7bacfbf87cda18.rlib /root/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/wasm32-unknown-emscripten/lib/liblibc-48b2b822b890a628.rlib /root/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/wasm32-unknown-emscripten/lib/liballoc-e119f963323764f2.rlib /root/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/wasm32-unknown-emscripten/lib/librustc_std_workspace_core-dccfe230458f39f9.rlib /root/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/wasm32-unknown-emscripten/lib/libcore-ff850c1994b8a1ec.rlib /root/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/wasm32-unknown-emscripten/lib/libcompiler_builtins-295fcaa60ab90f2f.rlib -lc-debug -L/root/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/wasm32-unknown-emscripten/lib -L/root/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/wasm32-unknown-emscripten/lib/self-contained --fatal-warnings -L/root/code/emsdk/upstream/emscripten/cache/sysroot/lib/wasm32-emscripten -lGL -lal -lhtml5 -lstubs-debug -lnoexit -lc-debug -ldlmalloc -lcompiler_rt -lc++ -lc++abi-debug -lsockets -mllvm -combiner-global-alias-analysis=false -mllvm -enable-emscripten-cxx-exceptions -mllvm -enable-emscripten-sjlj -mllvm -disable-lsr /tmp/tmpg1ciymx5libemscripten_js_symbols.so --export-if-defined=main --export-if-defined=__get_exception_message --export-if-defined=free --export-if-defined=__start_em_asm --export-if-defined=__stop_em_asm --export-if-defined=__start_em_lib_deps --export-if-defined=__stop_em_lib_deps --export-if-defined=__start_em_js --export-if-defined=__stop_em_js --export-if-defined=__main_argc_argv --export-if-defined=fflush --export=emscripten_stack_get_end --export=emscripten_stack_get_free --export=emscripten_stack_get_base --export=emscripten_stack_get_current --export=emscripten_stack_init --export=stackSave --export=stackRestore --export=stackAlloc --export=__errno_location --export=__get_temp_ret --export=__set_temp_ret --export=__cxa_is_pointer_type --export=__cxa_can_catch --export=__cxa_increment_exception_refcount --export=__cxa_decrement_exception_refcount --export=setThrew --export=__cxa_free_exception --export=__wasm_call_ctors --export=__get_exception_message --export=free --export-table -z stack-size=65536 --initial-memory=16777216 --max-memory=16777216 --no-entry --stack-first --table-base=1' failed (returned 1)
          

warning: `emsdk-demo` (bin "emsdk-demo") generated 1 warning
error: could not compile `emsdk-demo` (bin "emsdk-demo") due to previous error; 1 warning emitted```

</p>
</details>