[wasm-split] Set import namespace only when given in multi-split#7966
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Currently, in the case of two-way split, we set `config.importNamespace` only when `--import-namespace` option is given, and otherwise just use the default namespace "primary". But in the case of multi split, we set it regardless of whether the option is given, resulting in the "" namespace when no option is given. The default import namespace for multi-split was "" when the multi-split function was first added (WebAssembly#6943), so I'm not sure whether this difference was intentional. In case it wasn't, I think it makes sense to be consistent between two-way split and multi-split. So this in effect changes the import namespace in multi split tests from "" to `primary`. This also factors out the part that moves `WasmSplitOptions` into `Config` to a function.
aheejin
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Oct 11, 2025
| "namespace from which to import the secondary memory, if any.", | ||
| WasmSplitOption, | ||
| {Mode::Split, Mode::Instrument, Mode::MultiSplit}, | ||
| {Mode::Split, Mode::MultiSplit, Mode::Instrument}, |
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This just changed the order
tlively
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Oct 11, 2025
aheejin
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Jan 27, 2026
We weren't able to give empty strings as options like `--import-namespace=` or `--import-namespace=""` so far because 1. When `command-line.cpp` parses `--option=`, it parses the next option as its value. For example, if we have `wasm-split ... --import-namespace -o output.wasm`, it parses `-o` as the value for `--import-namespace`. 2. Even if we fix 1, many places in `wasm-split.cpp` checks for `if (options.optionName.size())` so the option with size 0 cannot be processed. This fixes them and allow `--import-namespace` and other similar options take an empty string for a value. Since WebAssembly#7966 changed the default primary export namespace to `primary`, acx_gallery failed to run (which I realized it only recently) and giving it `--import-namespace=""` didn't work because of the above reasons.
aheejin
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Jan 28, 2026
We weren't able to give empty strings as options like `--import-namespace=` or `--import-namespace=""` so far because 1. When `command-line.cpp` parses `--option=`, it parses the next option as its value. For example, if we have `wasm-split ... --import-namespace -o output.wasm`, it parses `-o` as the value for `--import-namespace`. 2. Even if we fix 1, many places in `wasm-split.cpp` checks for `if (options.optionName.size())` so the option with size 0 cannot be processed. This fixes them and allow `--import-namespace` and other similar options take an empty string for a value. Since #7966 changed the default primary export namespace to `primary`, acx_gallery failed to run (which I realized it only recently) because it assumed the empty string namespace, and giving it `--import-namespace=""` didn't work because of the above reasons.
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Currently, in the case of two-way split, we set
config.importNamespaceonly when--import-namespaceoption is given, and otherwise just use the default namespace "primary". But in the case of multi split, we set it regardless of whether the option is given, resulting in the "" namespace when no option is given.The default import namespace for multi-split was "" when the multi-split function was first added (#6943), so I'm not sure whether this difference was intentional.
binaryen/src/tools/wasm-split/wasm-split.cpp
Line 419 in a9a7f91
In case it wasn't, I think it makes sense to be consistent between two-way split and multi-split. So this in effect changes the import namespace in multi split tests from "" to
primary.This also factors out the part that moves
WasmSplitOptionsintoConfigto a function.