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@@ -574,6 +574,11 @@ file the calls between the modules become just normal calls inside a module, which allows them to be inlined, dead code eliminated, and so forth, potentially improving speed and size. +`wasm-merge` operates on normal wasm files. It differs from `wasm-ld` in that +respect, as `wasm-ld` operates on wasm *object* files. `wasm-merge` can help +in multi-toolchain situations where at least one of the toolchains does not use +wasm object files. + For example, imagine we have these two wasm files: ```wat @@ -709,6 +714,33 @@ merged.exports.main(); We still need to fetch and compile the merged wasm, and to provide it the JS import, but the work to connect two wasm modules is not needed any more. +#### Handling exports + +By default `wasm-merge` errors if there are overlapping export names. That is, +`wasm-merge` will automatically handle overlapping function names and so forth, +because those are not externally visible (the code still behaves the same), but +if we renamed exports then the outside would need to be modified to expect the +new export names, and so we error instead on such name conflicts. + +If you do want exports to be renamed, run `wasm-merge` with +`--rename-export-conflicts`. Later exports will have a suffix appended to them +to ensure they do not overlap with previous exports. The suffixes are +deterministic, so once you see what they are you can call them from the outside. + +Another option is to use `--skip-export-conflicts` which will simply skip later +exports that have conflicting names. For example, this can be useful in the +case where the first module is the only one that interacts with the outside and +the later modules just interact with the first module. + +#### Features + +`wasm-merge` uses the multi-memory and multi-table features. That is, if +multiple input modules each have a memory then the output wasm will have several +memories, and will depend on the multi-memory feature, which means that older +wasm VMs might not be able to run the wasm. (As a workaround for such older VMs +you can run `wasm-opt --multi-memory-lowering` to lower multiple memories into a +single one.) + ## Testing ``` |