<table border="1" cellspacing="0" cellpadding="8">
    <tr>
        <th>Issue</th>
        <td>
            <a href=https://github.com/llvm/llvm-project/issues/126919>126919</a>
        </td>
    </tr>

    <tr>
        <th>Summary</th>
        <td>
            [WebAssembly] Huge symbol name section in debug build
        </td>
    </tr>

    <tr>
      <th>Labels</th>
      <td>
            new issue
      </td>
    </tr>

    <tr>
      <th>Assignees</th>
      <td>
      </td>
    </tr>

    <tr>
      <th>Reporter</th>
      <td>
          stevenwdv
      </td>
    </tr>
</table>

<pre>
    # Problem
I'm getting a huge (**10 GiB**) `name` section containing symbols in our WebAssembly build, and I don't know if this is a bug or not, since with native builds the section is much smaller (323 MiB for the full binary).

# More context
It's so big that `WasmObjectFile` cannot successfully parse it anymore: the section is 10 GiB, which does not fit in a uint32, which causes `LEB is outside Varuint32 range` when reading, which happens in a `llvm-objcopy` command executed at the very last step of linking. This happens with with 32-bit and 64-bit builds.

I first thought this was #58555, but it appears that that is a different issue, my issue happens here:

https://github.com/llvm/llvm-project/blob/560149b5e3c891c64899e9912e29467a69dc3a4c/llvm/lib/Object/WasmObjectFile.cpp#L305-L314

<details>
<summary>Stack trace using Debug build</summary>

```
$ ~/llvm-project/build/bin/llvm-objcopy cpp/pep/cli/pepcli.wasm cpp/pep/cli/pepcli-noproducers.wasm --remove-section=producers
LLVM ERROR: LEB is outside Varuint32 range
PLEASE submit a bug report to https://github.com/llvm/llvm-project/issues/ and include the crash backtrace.
Stack dump:
0.      Program arguments: /home/swdv/llvm-project/build/bin/llvm-objcopy cpp/pep/cli/pepcli.wasm cpp/pep/cli/pepcli.wasm --remove-section=producers
 #0 0x00007e9a0cc06f31 llvm::sys::PrintStackTrace(llvm::raw_ostream&, int) /home/swdv/llvm-project/llvm/lib/Support/Unix/Signals.inc:804:11
 #1 0x00007e9a0cc0742b PrintStackTraceSignalHandler(void*) /home/swdv/llvm-project/llvm/lib/Support/Unix/Signals.inc:880:1
 #2 0x00007e9a0cc05426 llvm::sys::RunSignalHandlers() /home/swdv/llvm-project/llvm/lib/Support/Signals.cpp:105:5
 #3 0x00007e9a0cc07bed SignalHandler(int, siginfo_t*, void*) /home/swdv/llvm-project/llvm/lib/Support/Unix/Signals.inc:418:7
 #4 0x00007e9a0c045330 (/lib/x86_64-linux-gnu/libc.so.6+0x45330)
 #5 0x00007e9a0c09eb2c pthread_kill (/lib/x86_64-linux-gnu/libc.so.6+0x9eb2c)
 #6 0x00007e9a0c04527e raise (/lib/x86_64-linux-gnu/libc.so.6+0x4527e)
 #7 0x00007e9a0c0288ff abort (/lib/x86_64-linux-gnu/libc.so.6+0x288ff)
 #8 0x00007e9a0caca9b4 llvm::report_fatal_error(llvm::Twine const&, bool) /home/swdv/llvm-project/llvm/lib/Support/ErrorHandling.cpp:126:5
 #9 0x00007e9a0caca822 /home/swdv/llvm-project/llvm/lib/Support/ErrorHandling.cpp:84:3
#10 0x00007e9a0d5b9699 readVaruint32(llvm::object::WasmObjectFile::ReadContext&) /home/swdv/llvm-project/llvm/lib/Object/WasmObjectFile.cpp:160:10
#11 0x00007e9a0d5b6602 readSection(llvm::object::WasmSection&, llvm::object::WasmObjectFile::ReadContext&, llvm::object::WasmSectionOrderChecker&) /home/swdv/llvm-project/llvm/lib/Object/WasmObjectFile.cpp:312:12
#12 0x00007e9a0d5b63d7 llvm::object::WasmObjectFile::WasmObjectFile(llvm::MemoryBufferRef, llvm::Error&) /home/swdv/llvm-project/llvm/lib/Object/WasmObjectFile.cpp:377:10
#13 0x00007e9a0d5c04d2 std::__detail::_MakeUniq<llvm::object::WasmObjectFile>::__single_object std::make_unique<llvm::object::WasmObjectFile, llvm::MemoryBufferRef&, llvm::Error&>(llvm::MemoryBufferRef&, llvm::Error&) /usr/bin/../lib/gcc/x86_64-linux-gnu/13/../../../../include/c++/13/bits/unique_ptr.h:1070:34
#14 0x00007e9a0d5b5e2f llvm::object::ObjectFile::createWasmObjectFile(llvm::MemoryBufferRef) /home/swdv/llvm-project/llvm/lib/Object/WasmObjectFile.cpp:69:7
#15 0x00007e9a0d58fcbf llvm::object::ObjectFile::createObjectFile(llvm::MemoryBufferRef, llvm::file_magic, bool) /home/swdv/llvm-project/llvm/lib/Object/ObjectFile.cpp:203:12
#16 0x00007e9a0d5a1f50 llvm::object::SymbolicFile::createSymbolicFile(llvm::MemoryBufferRef, llvm::file_magic, llvm::LLVMContext*, bool) /home/swdv/llvm-project/llvm/lib/Object/SymbolicFile.cpp:71:12
#17 0x00007e9a0d400b65 llvm::object::createBinary(llvm::MemoryBufferRef, llvm::LLVMContext*, bool) /home/swdv/llvm-project/llvm/lib/Object/Binary.cpp:78:12
#18 0x00007e9a0d40106f llvm::object::createBinary(llvm::StringRef, llvm::LLVMContext*, bool) /home/swdv/llvm-project/llvm/lib/Object/Binary.cpp:117:8
#19 0x00005dbea7d09645 executeObjcopy(llvm::objcopy::ConfigManager&) /home/swdv/llvm-project/llvm/tools/llvm-objcopy/llvm-objcopy.cpp:173:10
#20 0x00005dbea7d08ee6 llvm_objcopy_main(int, char**, llvm::ToolContext const&) /home/swdv/llvm-project/llvm/tools/llvm-objcopy/llvm-objcopy.cpp:253:15
#21 0x00005dbea7d0d385 main /home/swdv/llvm-project/build/tools/llvm-objcopy/llvm-objcopy-driver.cpp:17:3
#22 0x00007e9a0c02a1ca (/lib/x86_64-linux-gnu/libc.so.6+0x2a1ca)
#23 0x00007e9a0c02a28b __libc_start_main (/lib/x86_64-linux-gnu/libc.so.6+0x2a28b)
#24 0x00005dbea7cc2845 _start (/home/swdv/llvm-project/build/bin/llvm-objcopy+0x34845)
Aborted (core dumped)
```
</details>

It seems that the reading code is correct, see https://github.com/llvm/llvm-project/issues/58555#issuecomment-2651122107. However, my question is: how did this section get this large in the first place?

I'm compiling with Release versions of the libraries we use, but compiling our own code as Debug. In the `name` section I can see symbol names upwards of 20 MB. (These contain lots of templates and repeated expanded types, also containing type_traits stuff etc. We use [RxCpp](https://github.com/ReactiveX/RxCpp), which uses a lot of nested templates, causing large symbol names, so that contributes to the problem.) I found that a workaround is to use `--strip-all`.

Still, why is this a problem with WebAssembly, and not so much with native builds, which just produce builds of around 323 MiB instead of the 10 GiB we get with WebAssembly?
</pre>
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