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Linking with extern function in Wasm #63562
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A-linkage
Area: linking into static, shared libraries and binaries
O-wasm
Target: WASM (WebAssembly), http://webassembly.org/
T-compiler
Relevant to the compiler team, which will review and decide on the PR/issue.
Comments
Hi, guys! Are there any updates? |
joelpalmer
added
A-linkage
Area: linking into static, shared libraries and binaries
C-tracking-issue
Category: An issue tracking the progress of sth. like the implementation of an RFC
T-compiler
Relevant to the compiler team, which will review and decide on the PR/issue.
and removed
C-tracking-issue
Category: An issue tracking the progress of sth. like the implementation of an RFC
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Sep 16, 2019
alexcrichton
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O-wasm
Target: WASM (WebAssembly), http://webassembly.org/
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Dec 16, 2019
Mark-Simulacrum
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Dec 19, 2019
…=eddyb Fix handling of wasm import modules and names The WebAssembly targets of rustc have weird issues around name mangling and import the same name from different modules. This all largely stems from the fact that we're using literal symbol names in LLVM IR to represent what a function is called when it's imported, and we're not using the wasm-specific `wasm-import-name` attribute. This in turn leads to two issues: * If, in the same codegen unit, the same FFI symbol is referenced twice then rustc, when translating to LLVM IR, will only reference one symbol from the first wasm module referenced. * There's also a bug in LLD [1] where even if two codegen units reference different modules, having the same symbol names means that LLD coalesces the symbols and only refers to one wasm module. Put another way, all our imported wasm symbols from the environment are keyed off their LLVM IR symbol name, which has lots of collisions today. This commit fixes the issue by implementing two changes: 1. All wasm symbols with `#[link(wasm_import_module = "...")]` are mangled by default in LLVM IR. This means they're all given unique names. 2. Symbols then use the `wasm-import-name` attribute to ensure that the WebAssembly file uses the correct import name. When put together this should ensure we don't trip over the LLD bug [1] and we also codegen IR correctly always referencing the right symbols with the right import module/name pairs. Closes rust-lang#50021 Closes rust-lang#56309 Closes rust-lang#63562 [1]: https://bugs.llvm.org/show_bug.cgi?id=44316
Centril
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Dec 20, 2019
…=eddyb Fix handling of wasm import modules and names The WebAssembly targets of rustc have weird issues around name mangling and import the same name from different modules. This all largely stems from the fact that we're using literal symbol names in LLVM IR to represent what a function is called when it's imported, and we're not using the wasm-specific `wasm-import-name` attribute. This in turn leads to two issues: * If, in the same codegen unit, the same FFI symbol is referenced twice then rustc, when translating to LLVM IR, will only reference one symbol from the first wasm module referenced. * There's also a bug in LLD [1] where even if two codegen units reference different modules, having the same symbol names means that LLD coalesces the symbols and only refers to one wasm module. Put another way, all our imported wasm symbols from the environment are keyed off their LLVM IR symbol name, which has lots of collisions today. This commit fixes the issue by implementing two changes: 1. All wasm symbols with `#[link(wasm_import_module = "...")]` are mangled by default in LLVM IR. This means they're all given unique names. 2. Symbols then use the `wasm-import-name` attribute to ensure that the WebAssembly file uses the correct import name. When put together this should ensure we don't trip over the LLD bug [1] and we also codegen IR correctly always referencing the right symbols with the right import module/name pairs. Closes rust-lang#50021 Closes rust-lang#56309 Closes rust-lang#63562 [1]: https://bugs.llvm.org/show_bug.cgi?id=44316
Centril
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Dec 20, 2019
…=eddyb Fix handling of wasm import modules and names The WebAssembly targets of rustc have weird issues around name mangling and import the same name from different modules. This all largely stems from the fact that we're using literal symbol names in LLVM IR to represent what a function is called when it's imported, and we're not using the wasm-specific `wasm-import-name` attribute. This in turn leads to two issues: * If, in the same codegen unit, the same FFI symbol is referenced twice then rustc, when translating to LLVM IR, will only reference one symbol from the first wasm module referenced. * There's also a bug in LLD [1] where even if two codegen units reference different modules, having the same symbol names means that LLD coalesces the symbols and only refers to one wasm module. Put another way, all our imported wasm symbols from the environment are keyed off their LLVM IR symbol name, which has lots of collisions today. This commit fixes the issue by implementing two changes: 1. All wasm symbols with `#[link(wasm_import_module = "...")]` are mangled by default in LLVM IR. This means they're all given unique names. 2. Symbols then use the `wasm-import-name` attribute to ensure that the WebAssembly file uses the correct import name. When put together this should ensure we don't trip over the LLD bug [1] and we also codegen IR correctly always referencing the right symbols with the right import module/name pairs. Closes rust-lang#50021 Closes rust-lang#56309 Closes rust-lang#63562 [1]: https://bugs.llvm.org/show_bug.cgi?id=44316
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Apr 28, 2020
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since rust-lang/rust#63562 fixed
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since rust-lang/rust#63562 fixed
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Labels
A-linkage
Area: linking into static, shared libraries and binaries
O-wasm
Target: WASM (WebAssembly), http://webassembly.org/
T-compiler
Relevant to the compiler team, which will review and decide on the PR/issue.
I am trying to use functions from an external module and importing them like that:
But if I have exported functions with the same names in my own module, there will be linked with these local functions (in these case these functions won't be in the import section of a compiled module). Is it possible to link with functions in external module having functions with the same name in your own?
POC can be found here.
Btw, in C it could be done in this way:
and works perfectly.
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