Report all declarations and definitions of unused functions by eduard-bagdasaryan · Pull Request #7 · measurement-factory/xunused

eduard-bagdasaryan · 2025-12-29T15:44:06Z

Report all declarations and all definitions of an unused function, from
all TUs. Prior to these changes, only the definition in the first TU and
only the declarations from the last TU were reported.

The reporting now also includes the last line number:

source.cc:3: warning: Function 'F' is unused
source.cc:2: note: declared here
source.cc:2: note: declaration ends here
source.cc:3: note: defined here
source.cc:5: note: definition ends here

These reports help automate unused code removal. They are especially
handy when a large project applies xunused for the first time.

This is useful for unused code removal automation. The reporting now has the last line number of declaration or definition: file.cc:8:12: warning: Function 'F' is unused file.cc:3:3: note: declared here

rousskov

Please add a test case to check the new functionality. Ideally, that test will have multiple definitions of the same function X and multiple declarations of the same function Y, where X and Y are the same (if possible) or different functions (otherwise).

main.cpp

Also report all definitions as well as all declarations.

eduard-bagdasaryan · 2026-01-05T12:02:19Z

Please add a test case to check the new functionality

Added.

rousskov

Please check updated PR title/description as well.

rousskov · 2026-01-05T19:12:05Z

tests/declaration-and-definition-reporting.test

+// CHECK-DAG: source2.cc:5:{{.*}}definition ends here
+
+//--- source1.cc
+#include <iostream>


Do we need to include this?

I added this extra line so that F() would not start with the first line (avoiding first/last values just in case).

I do not know what you mean by "avoiding first/last values". I think it would actually be good to test first-line position in one of the source files. In the other file (e.g., this one), let's add a comment instead (if it works):

Suggested change

#include <iostream>

// no "extern" declaration for F() in this source file

and remove #include from source2.cc.

rousskov · 2026-01-05T19:21:51Z

main.cpp

-    if (I.Definitions > 0 && I.Uses == 0) {
-      llvm::errs() << I.Filename << ":" << I.Line << ": warning:"
+    if (I.declaredOrDefined() && I.Uses == 0) {


I suspect that this I.Definitions > 0 condition was meant to skip various functions "external" to the project being scanned (e.g., a system function that the project forward-declares instead of including an appropriate standard header file) and never-defined functions (e.g., forgotten/unused forward declarations of project-specific functions that no longer exist). We did not report such functions as unused prior to this PR. I do not think this PR should start reporting those functions (even though we would like the second category to eventually be included in these "unused" reports).

Ok, I restored the previous condition (i.e., its equivalent).

main.cpp

Also polished the test case.

eduard-bagdasaryan

Done (ebe117b).

eduard-bagdasaryan · 2026-01-07T21:31:17Z

main.cpp

-    if (I.Definitions > 0 && I.Uses == 0) {
-      llvm::errs() << I.Filename << ":" << I.Line << ": warning:"
+    if (I.declaredOrDefined() && I.Uses == 0) {


Ok, I restored the previous condition (i.e., its equivalent).

main.cpp

eduard-bagdasaryan · 2026-01-07T21:36:47Z

tests/declaration-and-definition-reporting.test

+// CHECK-DAG: source2.cc:5:{{.*}}definition ends here
+
+//--- source1.cc
+#include <iostream>


main.cpp

rousskov · 2026-01-08T21:30:06Z

main.cpp

+  DefInfo(const size_t uses, const FunctionDecl *F, const SourceManager &SM)
+      : Uses(uses), Name(F->getQualifiedNameAsString()) {}


In official code, {0,1} and {1,0} construction more-or-less made sense. This PR breaks that symmetry, making constructor-calling code even less readable. I suggest removing uses from the second constructor:

Suggested change

DefInfo(const size_t uses, const FunctionDecl *F, const SourceManager &SM)

: Uses(uses), Name(F->getQualifiedNameAsString()) {}

// Use this constructor when you find a definition of a never-seen-before function

DefInfo(const FunctionDecl * const F, const SourceManager &SM)

: Uses(0), Name(F->getQualifiedNameAsString()) {}

main.cpp

rousskov · 2026-01-08T21:32:49Z

main.cpp

+  DefInfo(const size_t uses, const FunctionDecl *F, const SourceManager &SM)
+      : Uses(uses), Name(F->getQualifiedNameAsString()) {}
+
+  bool defined() const { return !Definitions.empty(); }


foo.defined() looks a bit odd in source code, as if foo itself is "undefined" in some cases.

Suggested change

bool defined() const { return !Definitions.empty(); }

bool sawDefinition() const { return !Definitions.empty(); }

main.cpp

rousskov · 2026-01-08T21:38:58Z

main.cpp

+      auto &destination = R->doesThisDeclarationHaveABody() ? Definitions : Declarations;
+      destination.emplace_back(R, SM);


Suggested change

auto &destination = R->doesThisDeclarationHaveABody() ? Definitions : Declarations;

destination.emplace_back(R, SM);

auto &ds = R->doesThisDeclarationHaveABody() ? Definitions : Declarations;

ds.emplace_back(R, SM);

eduard-bagdasaryan

Adjusted (b233740).

main.cpp

eduard-bagdasaryan · 2026-01-10T10:36:42Z

main.cpp

+  DefInfo(const size_t uses, const FunctionDecl *F, const SourceManager &SM)
+      : Uses(uses), Name(F->getQualifiedNameAsString()) {}


eduard-bagdasaryan · 2026-01-10T10:37:39Z

main.cpp

+  DefInfo(const size_t uses, const FunctionDecl *F, const SourceManager &SM)
+      : Uses(uses), Name(F->getQualifiedNameAsString()) {}
+
+  bool defined() const { return !Definitions.empty(); }


eduard-bagdasaryan · 2026-01-10T10:39:47Z

main.cpp

+      auto &destination = R->doesThisDeclarationHaveABody() ? Definitions : Declarations;
+      destination.emplace_back(R, SM);


main.cpp

rousskov · 2026-01-12T16:37:02Z

main.cpp

-  size_t Definitions;
+  explicit DefInfo(const size_t uses) : Uses(uses) {}
+  // Use this constructor when you find a use of a never-seen-before function
+  DefInfo(const FunctionDecl *F, const SourceManager &SM)


Suggested change

DefInfo(const FunctionDecl *F, const SourceManager &SM)

explicit DefInfo(const FunctionDecl * const F)

rousskov · 2026-01-12T16:39:21Z

main.cpp

-
-      it_inserted.first->second.Declarations = getDeclarations(F, SM);
+      const auto it_inserted = AllDecls.emplace(std::move(USR), DefInfo(F, SM));
+      const auto &defInfo = it_inserted.first->second;


defInfo is unused, right?

Suggested change

const auto &defInfo = it_inserted.first->second;

main.cpp

rousskov · 2026-01-12T16:46:00Z

main.cpp

+  unsigned StartLine;
+  unsigned EndLine;


Let's avoid "end" because STL end() cannot be dereferenced, but this offset can be.

Suggested change

unsigned StartLine;

unsigned EndLine;

unsigned FirstLine;

unsigned LastLine; // same as FirstLine for single-line code

eduard-bagdasaryan

Done at 4ad9883.

main.cpp

eduard-bagdasaryan · 2026-01-13T13:20:01Z

main.cpp

-  size_t Definitions;
+  explicit DefInfo(const size_t uses) : Uses(uses) {}
+  // Use this constructor when you find a use of a never-seen-before function
+  DefInfo(const FunctionDecl *F, const SourceManager &SM)


eduard-bagdasaryan · 2026-01-13T13:20:40Z

main.cpp

-
-      it_inserted.first->second.Declarations = getDeclarations(F, SM);
+      const auto it_inserted = AllDecls.emplace(std::move(USR), DefInfo(F, SM));
+      const auto &defInfo = it_inserted.first->second;


eduard-bagdasaryan · 2026-01-13T13:21:00Z

main.cpp

+  unsigned StartLine;
+  unsigned EndLine;


Duplicated declarations could be stored into DefInfo::Declarations when parsing different TUs. This is the branch-introduced problem: before the PR changes, the Declarations vector was not accumulated but always overwritten by the current TU results.

DefInfo::Name was never initialized when DefInfo was constructed with the first constructor (i.e., when the function's call had been parsed before its declaration/definition).

* Normalize absolute paths to exclude duplicates * Correctly find the beginning of templates * Corectly find the end of function declarations with macro

However, such false possitives still are possible: //void G(); void F();

Report unused declaration and definition source code lines

fbc1c44

This is useful for unused code removal automation. The reporting now has the last line number of declaration or definition: file.cc:8:12: warning: Function 'F' is unused file.cc:3:3: note: declared here

rousskov requested changes Dec 29, 2025

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main.cpp Outdated Show resolved Hide resolved

main.cpp Outdated Show resolved Hide resolved

Split the reporting and added a test

f567928

Also report all definitions as well as all declarations.

Added a TODO

c56f769

rousskov changed the title ~~Report unused declaration and definition source code lines~~ Report all declarations and definitions of unused functions Jan 5, 2026

rousskov requested changes Jan 5, 2026

View reviewed changes

Refactored, addressing a PR-added TODO

ebe117b

Also polished the test case.

eduard-bagdasaryan commented Jan 7, 2026

View reviewed changes

rousskov reviewed Jan 7, 2026

View reviewed changes

main.cpp Outdated Show resolved Hide resolved

Simplified, removing DefInfo::DefLocation

aa462ff

rousskov requested changes Jan 8, 2026

View reviewed changes

eduard-bagdasaryan added 3 commits January 10, 2026 13:25

Reverted DeclLoc::Filename type back to SmallString<128>

9f95e54

Polished, addressing review comments

b233740

Report the last of DefInfo::Definitions, as before

d3b9c2e

eduard-bagdasaryan commented Jan 10, 2026

View reviewed changes

eduard-bagdasaryan added 2 commits January 10, 2026 14:43

Merged from master

8cd0c28

Improved const-correctness

d1117e4

rousskov requested changes Jan 12, 2026

View reviewed changes

eduard-bagdasaryan added 2 commits January 13, 2026 16:25

Polished and removed stale code

4ad9883

Merged from main

a00656c

eduard-bagdasaryan commented Jan 13, 2026

View reviewed changes

eduard-bagdasaryan added 6 commits January 31, 2026 00:26

Fixed the empty function name problem

410f81e

DefInfo::Name was never initialized when DefInfo was constructed with the first constructor (i.e., when the function's call had been parsed before its declaration/definition).

Several fixes:

2e1279c

* Normalize absolute paths to exclude duplicates * Correctly find the beginning of templates * Corectly find the end of function declarations with macro

Determine and report comment locations

eefcc59

Do not misattribute distant comments

09d31fe

However, such false possitives still are possible: //void G(); void F();

Count all function 'uses' instead of just 1

9ed3d71

	#include <iostream>
	// no "extern" declaration for F() in this source file

		DefInfo(const size_t uses, const FunctionDecl *F, const SourceManager &SM)
		: Uses(uses), Name(F->getQualifiedNameAsString()) {}

-  DefInfo(const size_t uses, const FunctionDecl *F, const SourceManager &SM)
-      : Uses(uses), Name(F->getQualifiedNameAsString()) {}
+  // Use this constructor when you find a definition of a never-seen-before function
+  DefInfo(const FunctionDecl * const F, const SourceManager &SM)
+      : Uses(0), Name(F->getQualifiedNameAsString()) {}

	bool defined() const { return !Definitions.empty(); }
	bool sawDefinition() const { return !Definitions.empty(); }

		auto &destination = R->doesThisDeclarationHaveABody() ? Definitions : Declarations;
		destination.emplace_back(R, SM);

	DefInfo(const FunctionDecl *F, const SourceManager &SM)
	explicit DefInfo(const FunctionDecl * const F)

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eduard-bagdasaryan commented Dec 29, 2025 • edited by rousskov Loading Uh oh! There was an error while loading. Please reload this page.

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eduard-bagdasaryan commented Jan 5, 2026

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eduard-bagdasaryan commented Dec 29, 2025 •

edited by rousskov

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