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[wasm-merge] Make empty function names explicit with --output-manifest #8871

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Merged
aheejin merged 3 commits into from
Jun 28, 2026
+38 −4
Merged

[wasm-merge] Make empty function names explicit with --output-manifest #8871

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5f8fe3c
[wasm-merge] Make empty function names explicit with --output-manifest
aheejin Jun 25, 2026
72a8892
Move if (!manifestFile.empty())
aheejin Jun 28, 2026
434fa88
typo
aheejin Jun 28, 2026
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13 changes: 9 additions & 4 deletions src/tools/wasm-merge.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -852,10 +852,15 @@ Input source maps can be specified by adding an -ism option right after the modu
// The functions in the module have been renamed and copied rather than
// moved, so we can get their final names directly. (We don't need this
// for the first module because it does not appear in the manifest.)
auto& funcs = moduleFuncs[inputFileName];
for (auto& func : currModule->functions) {
if (!func->imported()) {
funcs.push_back(func->name);
if (!manifestFile.empty()) {

@aheejin aheejin Jun 28, 2026

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NFC: I wrapped the whole for loop with if(!manifstFile.empty()), given that funcs will only be used for the output manifest file generation.

auto& funcs = moduleFuncs[inputFileName];
for (auto& func : currModule->functions) {
if (!func->imported()) {
funcs.push_back(func->name);
// Even if the function name is empty, if we were to put it in the
// output manifest, it has to be emitted in the name section.
merged.getFunction(func->name)->hasExplicitName = true;

@tlively tlively Jun 27, 2026

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The function might have been renamed when it was copied to the merged module, so func->name might refer to a different function, right? I think we have to make the name explicit at the point where we add the copied function to the merged module.

@aheejin aheejin Jun 28, 2026

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Renaming is done in in-place currModule before merging, so it will refer to the same function.

binaryen/src/tools/wasm-merge.cpp

Lines 647 to 649 in d39a6d8

// Rename things in the input module so that there are no conflicts with names
// in the merged module. We do so in place for efficiency.
renameInputItems(input);

}
}
}

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29 changes: 29 additions & 0 deletions test/lit/merge/manifest-explicit-name.wat
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Original file line number Diff line number Diff line change
@@ -0,0 +1,29 @@
;; RUN: wasm-merge %s first %s second --rename-export-conflicts --output-manifest %t.manifest -o %t.wasm
;; RUN: cat %t.manifest | filecheck %s
;; RUN: wasm-dis %t.wasm -o - | filecheck %s --check-prefix MERGED

;; This tests if the internal names of empty function names are correctly
;; preserved in the name section so that they can match the names in the
;; manifest file.

;; CHECK: second
;; CHECK-NEXT: 0_1
;; CHECK-NEXT:

;; MERGED: (module
;; MERGED-NEXT: (type $0 (func))
;; MERGED-NEXT: (export "foo" (func $0))
;; MERGED-NEXT: (export "foo_1" (func $0_1))
;; MERGED-NEXT: (func $0
;; MERGED-NEXT: (nop)
;; MERGED-NEXT: )
;; MERGED-NEXT: (func $0_1
;; MERGED-NEXT: (nop)
;; MERGED-NEXT: )
;; MERGED-NEXT: )

(module
(func (export "foo")
nop
)
)
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