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[wasm] Export cDAC contract descriptor getter on non-emscripten wasm (wasi-sdk) #131241

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Merged
lewing merged 3 commits into from
Jul 25, 2026
Merged

[wasm] Export cDAC contract descriptor getter on non-emscripten wasm (wasi-sdk) #131241

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[wasm] Export cDAC contract descriptor getter on non-emscripten wasm …
lewing Jul 22, 2026
2556363
Potential fix for pull request finding
lewing Jul 22, 2026
d399819
[wasm] Key the descriptor getter export on __wasm__, not TARGET_WASM
lewing Jul 24, 2026
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26 changes: 23 additions & 3 deletions src/coreclr/debug/datadescriptor-shared/contract-descriptor.c.in
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Original file line number Diff line number Diff line change
Expand Up @@ -30,13 +30,33 @@ struct ContractDescriptor CONTRACT_NAME = {
// Due to linking order, the export may also need to be added to
// the EXPORTED_FUNCTIONS setting for emcc.
// See https://emscripten.org/docs/getting_started/FAQ.html#why-do-functions-in-my-c-c-source-code-vanish-when-i-compile-to-webassembly
#define _GETTER_NAME(exportname) Get ## exportname
#define GETTER_NAME(exportname) _GETTER_NAME(exportname)
#define _GETTER_NAME_STR(exportname) "Get" #exportname
#define GETTER_NAME_STR(exportname) _GETTER_NAME_STR(exportname)
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lewing marked this conversation as resolved.

#if defined(EXPORT_CONTRACT) && defined(__EMSCRIPTEN__)
#include <emscripten.h>

#define _GETTER_NAME(exportname) Get ## exportname
#define GETTER_NAME(exportname) _GETTER_NAME(exportname)
extern void* EMSCRIPTEN_KEEPALIVE GETTER_NAME(CONTRACT_NAME)()
{
return (void*)&CONTRACT_NAME;
}
#endif // EXPORT_CONTRACT && __EMSCRIPTEN__
#elif defined(EXPORT_CONTRACT) && defined(__wasm__)
// Non-emscripten wasm (e.g. wasi-sdk): export the getter with an explicit export name so the
// descriptor symbol is both reachable by a native host and, critically, kept alive by the linker.
// Without an export rooting it, --gc-sections removes the descriptor from the final module (the
// emscripten path above relies on EMSCRIPTEN_KEEPALIVE for the same reason).
//
// This intentionally keys on the compiler-provided __wasm__ rather than the CoreCLR TARGET_WASM
// define. datadescriptor-shared is compiled by multiple consumers and TARGET_WASM (set only by
// CoreCLR's configurecompiler.cmake, and gated on IGNORE_DEFAULT_TARGET_ARCH) is not guaranteed to
// reach every one of them. Since the whole point of this branch is to keep the descriptor alive on
// any wasm toolchain, it must depend on a macro that is always defined when targeting wasm; __wasm__
// is set by the compiler itself for exactly that.
__attribute__((export_name(GETTER_NAME_STR(CONTRACT_NAME))))
void* GETTER_NAME(CONTRACT_NAME)()
{
return (void*)&CONTRACT_NAME;
}
#endif // EXPORT_CONTRACT && (__EMSCRIPTEN__ || __wasm__)