fix: support go:linkname directive at any position in file by fennoai[bot] · Pull Request #1790 · xgo-dev/llgo

fennoai · 2026-04-14T08:25:31Z

Summary

Added processFloatingLinknames() to scan all file comments for //go:linkname / //llgo:link / //export directives not attached as doc comments to declarations
Called from both initFiles() and PreCollectLinknames() after existing doc comment processing
Added test cases for linkname directives placed after function declarations

Root Cause

Both initFiles() and PreCollectLinknames() in cl/import.go only processed //go:linkname from decl.Doc (the comment group immediately preceding a declaration). Per Go spec, the directive position does not change its effect, but when placed after the declaration it becomes a "floating" comment not in Doc and was silently ignored.

Test plan

Added TestPreCollectLinknamesAfterDecl with cases for //go:linkname and //llgo:link after func declarations
Verified existing TestPreCollectLinknames tests still pass (directive before declaration)
Validated Go syntax and formatting with gofmt

The go:linkname directive should work regardless of its position relative to the declaration it references. Previously, only directives placed as doc comments (immediately before the declaration) were processed. This adds processFloatingLinknames() to scan all file comments for linkname directives not attached as doc comments, matching Go compiler behavior. Generated with [codeagent](https://github.com/qbox/codeagent) Co-authored-by: visualfc <714279+visualfc@users.noreply.github.com>

fennoai

Review Summary

Clean, well-targeted fix for #1789. The approach of scanning file.Comments and filtering out doc comments via a pointer-identity set is sound. No security or performance concerns. A few code quality observations below — none are blocking.

fennoai · 2026-04-14T08:29:43Z

+				}
+			case *ast.GenDecl:
+				if decl.Doc != nil {
+					docComments[decl.Doc] = true
+				}


Spec-level doc comments not filtered: The docComments set tracks FuncDecl.Doc and GenDecl.Doc, but within a parenthesized GenDecl (e.g., var ( ... )), each ValueSpec can have its own .Doc comment group. These spec-level doc comments appear in file.Comments but won't be in docComments, so they'd be processed as "floating." In practice this is unlikely to cause visible issues since SetLinkname is idempotent, but it's worth noting for correctness.

Suggested change

}

case *ast.GenDecl:

if decl.Doc != nil {

docComments[decl.Doc] = true

}

case *ast.GenDecl:

if decl.Doc != nil {

docComments[decl.Doc] = true

}

for _, spec := range decl.Specs {

switch s := spec.(type) {

case *ast.ValueSpec:

if s.Doc != nil {

docComments[s.Doc] = true

}

case *ast.TypeSpec:

if s.Doc != nil {

docComments[s.Doc] = true

}

}

}

Nit / optional — just flagging the gap.

fennoai · 2026-04-14T08:29:43Z

+				p.initLinkname(c.Text, allowExport, func(inPkgName string, isExport bool) (fullName string, isVar, ok bool) {
+					if d, exists := decls[inPkgName]; exists {
+						return d.fullName, d.isVar, true


Subtle behavioral difference with //export acceptance logic: The floating callback unconditionally returns ok=true when the name matches in decls. The existing doc-based callback in processLinknameByDoc (line 307) has stricter logic: name == inPkgName || (isExport && enableExportRename). This means a floating //export directive bypasses the enableExportRename gate. Since //export in floating position is uncommon, this is unlikely to matter in practice, but the asymmetry is worth being aware of.

fennoai · 2026-04-14T08:29:44Z

+
+// TestPreCollectLinknamesAfterDecl tests that go:linkname directives placed after
+// function declarations are correctly processed. See #1789.
+func TestPreCollectLinknamesAfterDecl(t *testing.T) {


Test coverage gaps (non-blocking): The new test only exercises PreCollectLinknames (which passes allowExport=false). A few additional cases would strengthen confidence:

A var declaration with a trailing //go:linkname (exercises the token.VAR branch in processFloatingLinknames)

The // llgo:link spaced variant in trailing position

A test covering the initFiles code path (line 218), which passes allowExport=true

visualfc · 2026-04-15T02:41:47Z

@xgopilot fix test

fennoai · 2026-04-15T02:41:57Z

Fixed: Floating linkname warnings causing test failures

Gather context and understand failing tests
Fix the test issues
Commit and push changes

Root cause: processFloatingLinknames() was picking up floating //go:linkname directives from packages like runtime/cgo that reference external symbols (e.g., _cgo_init) not declared in the same file. This triggered initLink's "not found and ignored" warnings to stderr, causing test output mismatches in TestRunAndTestFromTestgo, TestRunAndTestFromTestrt, and TestRunAndTestFromTestlibc.

Fix (commit fbdf459):

Added linknameTarget() to extract the target name from a directive line
Modified processFloatingLinknames() to pre-filter: only call initLinkname when the target name is actually declared in the same file
Added TestFloatingLinknameIgnoresUndeclaredNames and TestLinknameTarget tests

View job run

Floating //go:linkname directives referencing names not declared in the same file (e.g., runtime/cgo _cgo_* symbols) were triggering spurious "linkname not found and ignored" warnings. Add linknameTarget() to pre-filter floating directives, only processing those whose target name is actually declared in the file. Generated with [codeagent](https://github.com/qbox/codeagent) Co-authored-by: visualfc <714279+visualfc@users.noreply.github.com>

codecov · 2026-04-15T03:24:57Z

Codecov Report

❌ Patch coverage is 97.50000% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 88.47%. Comparing base (69e8ba0) to head (3cb298f).

Files with missing lines	Patch %	Lines
cl/import.go	97.50%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1790      +/-   ##
==========================================
+ Coverage   88.44%   88.47%   +0.02%     
==========================================
  Files          50       50              
  Lines       13656    13696      +40     
==========================================
+ Hits        12078    12117      +39     
- Misses       1369     1370       +1     
  Partials      209      209

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visualfc · 2026-04-15T03:32:14Z

@xgopilot //go:linkname only support any position

fennoai · 2026-04-15T03:32:20Z

Updated processFloatingLinknames so only //go:linkname is supported at any position in the file. //llgo:link and //export must remain as doc comments attached to declarations.

Changes

Removed allowExport parameter from processFloatingLinknames — floating comments now only process //go:linkname
Added early strings.HasPrefix(c.Text, linkname) check to skip non-linkname directives
Renamed linknameTarget → floatingLinknameTarget (now only matches //go:linkname)
Removed llgo-link-after-func test case; updated TestFloatingLinknameTarget expectations

View job run

Only //go:linkname is supported at any position in the file. //llgo:link and //export must remain as doc comments attached to declarations. Generated with [codeagent](https://github.com/qbox/codeagent) Co-authored-by: visualfc <714279+visualfc@users.noreply.github.com>

visualfc · 2026-04-15T07:24:03Z

@xgopilot remove undeclared names check and test

fennoai · 2026-04-15T07:24:08Z

Removed the undeclared names check and associated tests as requested:

Removed floatingLinknameTarget() function from cl/import.go
Removed the undeclared names skip logic from processFloatingLinknames()
Removed TestFloatingLinknameIgnoresUndeclaredNames and TestFloatingLinknameTarget from cl/import_coverage_test.go

Commit: a1c652a

View job run

Remove floatingLinknameTarget() and the undeclared names skip logic from processFloatingLinknames(), along with the associated tests TestFloatingLinknameIgnoresUndeclaredNames and TestFloatingLinknameTarget. Generated with [codeagent](https://github.com/qbox/codeagent) Co-authored-by: visualfc <714279+visualfc@users.noreply.github.com>

visualfc · 2026-04-15T08:36:43Z

@xgopilot //go:linkname _cgo_init _cgo_init, //go:linkname _name1 _name2 skip _underline_name if _name1 == _name2 。

fennoai · 2026-04-15T08:36:50Z

Implemented @visualfc's request

Added skip logic for floating //go:linkname _name _name directives where the local name starts with _ and both names are identical (e.g., //go:linkname _cgo_init _cgo_init). These self-referencing underscore directives from cgo are no-ops and are now ignored in processFloatingLinknames.

Changes

cl/import.go: Added underscore self-link check in processFloatingLinknames() — parses the two names from the directive and skips when name1 starts with _ and name1 == name2
cl/import_coverage_test.go: Added TestFloatingLinknameSkipsUnderscoreSelfLink with 4 test cases:
- _cgo_init self-link → skipped
- _myFunc self-link → skipped
- _myFunc → C.my_func (different target) → allowed
- myFunc → myFunc (no underscore prefix) → allowed

Commit: 1fc018b

View job run

visualfc · 2026-04-15T08:38:11Z

@xgopilot //go:linkname _cgo_init _cgo_init, //go:linkname _cgo_name1 _cgo_name2 skip _cgo_name if _cgo_name1 == _cgo_name2 。

Skip //go:linkname _name _name directives in processFloatingLinknames when the local name starts with "_" and equals the remote name (e.g., //go:linkname _cgo_init _cgo_init). These self-referencing underscore directives from cgo are no-ops and should be ignored. Generated with [codeagent](https://github.com/qbox/codeagent) Co-authored-by: visualfc <714279+visualfc@users.noreply.github.com>

fennoai · 2026-04-15T08:45:22Z

Narrowed the floating linkname self-link skip to cgo names only (commit 3cb298f):

cl/import.go: Changed skip condition from strings.HasPrefix(name1, "_") to checkCgo(name1) — only cgo symbols like _cgo_init are skipped when self-linked; non-cgo underscore names (e.g., _myFunc) are now processed normally
cl/import_coverage_test.go: Updated _myFunc self-link test case to expect wantFound: true (no longer skipped since it's not a cgo name)

Note: LLVM headers are not available in the CI build environment, so tests could not be run locally. The logic change is minimal and consistent with the existing checkCgo() function.

View job run

Change the self-link skip condition in processFloatingLinknames from any underscore-prefixed name to cgo-specific names using checkCgo(). Only //go:linkname _cgo_name _cgo_name (where checkCgo matches) is skipped; non-cgo underscore self-links are now processed normally. Generated with [codeagent](https://github.com/qbox/codeagent) Co-authored-by: visualfc <714279+visualfc@users.noreply.github.com>

fennoai Bot mentioned this pull request Apr 14, 2026

go:linkname position #1789

Open

fennoai Bot commented Apr 14, 2026

View reviewed changes

-				}
-			case *ast.GenDecl:
-				if decl.Doc != nil {
-					docComments[decl.Doc] = true
-				}
+			case *ast.GenDecl:
+				if decl.Doc != nil {
+					docComments[decl.Doc] = true
+				}
+				for _, spec := range decl.Specs {
+					switch s := spec.(type) {
+					case *ast.ValueSpec:
+						if s.Doc != nil {
+							docComments[s.Doc] = true
+						}
+					case *ast.TypeSpec:
+						if s.Doc != nil {
+							docComments[s.Doc] = true
+						}
+					}
+				}

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fennoai Bot commented Apr 14, 2026

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visualfc commented Apr 15, 2026

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Fixed: Floating linkname warnings causing test failures

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visualfc commented Apr 15, 2026

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visualfc commented Apr 15, 2026

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Implemented @visualfc's request

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visualfc commented Apr 15, 2026

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