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If a macro is used within a function, the code inside the macro
doesn't make the code less readable. Instead, for a reader a macro is
more like a function that is called. Thus the code inside a macro
shouldn't increase the complexity of the function in which it is called.
Thus the flag 'IgnoreMacros' is added. If set to 'true' code inside
macros isn't considered during analysis.
This isn't perfect, as now the code of a macro isn't considered at all,
even if it has a high cognitive complexity itself. It might be better if
a macro is considered in the analysis like a function and gets its own
cognitive complexity. Implementing such an analysis seems to be very
complex (if possible at all with the given AST), so we give the user the
option to either ignore macros completely or to let the expanded code
count to the calling function's complexity.
See the code example from vgeof (originally added as note in
https://reviews.llvm.org/D96281)
bool doStuff(myClass* objectPtr){
if(objectPtr == nullptr){
LOG_WARNING("empty object");
return false;
}
if(objectPtr->getAttribute() == nullptr){
LOG_WARNING("empty object");
return false;
}
use(objectPtr->getAttribute());
}
The LOG_WARNING macro itself might have a high complexity, but it do not make
the
the function more complex to understand like e.g. a 'printf'.
By default 'IgnoreMacros' is set to 'false', which is the original behavior of
the check.
Repository:
rG LLVM Github Monorepo
https://reviews.llvm.org/D98070
Files:
clang-tools-extra/clang-tidy/readability/FunctionCognitiveComplexityCheck.cpp
clang-tools-extra/clang-tidy/readability/FunctionCognitiveComplexityCheck.h
clang-tools-extra/docs/clang-tidy/checks/readability-function-cognitive-complexity.rst
clang-tools-extra/test/clang-tidy/checkers/readability-function-cognitive-complexity-flags.cpp
Index: clang-tools-extra/test/clang-tidy/checkers/readability-function-cognitive-complexity-flags.cpp
===================================================================
--- clang-tools-extra/test/clang-tidy/checkers/readability-function-cognitive-complexity-flags.cpp
+++ clang-tools-extra/test/clang-tidy/checkers/readability-function-cognitive-complexity-flags.cpp
@@ -10,9 +10,18 @@
// RUN: value: 5}, \
// RUN: {key: readability-function-cognitive-complexity.DescribeBasicIncrements, \
// RUN: value: "false"} ]}'
+// RUN: %check_clang_tidy -check-suffix=IGNORE-MACROS %s readability-function-cognitive-complexity %t -- \
+// RUN: -config='{CheckOptions: \
+// RUN: [{key: readability-function-cognitive-complexity.Threshold, \
+// RUN: value: 0}, \
+// RUN: {key: readability-function-cognitive-complexity.IgnoreMacros, \
+// RUN: value: "true"}, \
+// RUN: {key: readability-function-cognitive-complexity.DescribeBasicIncrements, \
+// RUN: value: "false"} ]}'
void func_of_complexity_4() {
// CHECK-NOTES: :[[@LINE-1]]:6: warning: function 'func_of_complexity_4' has cognitive complexity of 4 (threshold 0) [readability-function-cognitive-complexity]
+ // CHECK-NOTES-IGNORE-MACROS: :[[@LINE-2]]:6: warning: function 'func_of_complexity_4' has cognitive complexity of 4 (threshold 0) [readability-function-cognitive-complexity]
if (1) {
if (1) {
}
@@ -34,9 +43,41 @@
void function_with_macro() {
// CHECK-NOTES: :[[@LINE-1]]:6: warning: function 'function_with_macro' has cognitive complexity of 11 (threshold 0) [readability-function-cognitive-complexity]
// CHECK-NOTES-THRESHOLD5: :[[@LINE-2]]:6: warning: function 'function_with_macro' has cognitive complexity of 11 (threshold 5) [readability-function-cognitive-complexity]
+ // CHECK-NOTES-IGNORE-MACROS: :[[@LINE-3]]:6: warning: function 'function_with_macro' has cognitive complexity of 1 (threshold 0) [readability-function-cognitive-complexity]
MacroOfComplexity10;
if (1) {
}
}
+
+#define noop \
+ {}
+
+#define SomeMacro(x) \
+ if (1) { \
+ x; \
+ }
+
+void func_macro_1() {
+ // CHECK-NOTES: :[[@LINE-1]]:6: warning: function 'func_macro_1' has cognitive complexity of 2 (threshold 0) [readability-function-cognitive-complexity]
+ // CHECK-NOTES-IGNORE-MACROS: :[[@LINE-2]]:6: warning: function 'func_macro_1' has cognitive complexity of 1 (threshold 0) [readability-function-cognitive-complexity]
+
+ if (1) {
+ }
+ SomeMacro(noop);
+}
+
+void func_macro_2() {
+ // CHECK-NOTES: :[[@LINE-1]]:6: warning: function 'func_macro_2' has cognitive complexity of 4 (threshold 0) [readability-function-cognitive-complexity]
+ // CHECK-NOTES-IGNORE-MACROS: :[[@LINE-2]]:6: warning: function 'func_macro_2' has cognitive complexity of 1 (threshold 0) [readability-function-cognitive-complexity]
+
+ if (1) {
+ }
+ // Note that if the IgnoreMacro option is set to 'true', currently also macro
+ // arguments are ignored. Optimally, macros should be treated like function
+ // calls, i.e. the arguments account to the complexity so that the overall
+ // complexity of this function is 2 (1 for the if statement above + 1 for
+ // the if statement in the argument).
+ SomeMacro(if (1) { noop; });
+}
Index: clang-tools-extra/docs/clang-tidy/checks/readability-function-cognitive-complexity.rst
===================================================================
--- clang-tools-extra/docs/clang-tidy/checks/readability-function-cognitive-complexity.rst
+++ clang-tools-extra/docs/clang-tidy/checks/readability-function-cognitive-complexity.rst
@@ -24,6 +24,12 @@
`if` statement, etc.) which contributes to that complexity. See also the
examples below. Default is `true`.
+.. option:: IgnoreMacros
+
+ If set to `true`, the check will ignore code inside macros. Note, that also
+ any macro arguments are ignored, even if they should count to the complexity.
+ Default is `false`.
+
Building blocks
---------------
Index: clang-tools-extra/clang-tidy/readability/FunctionCognitiveComplexityCheck.h
===================================================================
--- clang-tools-extra/clang-tidy/readability/FunctionCognitiveComplexityCheck.h
+++ clang-tools-extra/clang-tidy/readability/FunctionCognitiveComplexityCheck.h
@@ -26,6 +26,8 @@
/// diagnostics on every piece of code (loop, `if` statement, etc.) which
/// contributes to that complexity.
// Default is `true`
+/// * `IgnoreMacros` - if set to `true`, the check will ignore code inside
+/// macros. Default is `false`.
///
/// For the user-facing documentation see:
/// http://clang.llvm.org/extra/clang-tidy/checks/readability-function-cognitive-complexity.html
@@ -43,6 +45,7 @@
private:
const unsigned Threshold;
const bool DescribeBasicIncrements;
+ const bool IgnoreMacros;
};
} // namespace readability
Index: clang-tools-extra/clang-tidy/readability/FunctionCognitiveComplexityCheck.cpp
===================================================================
--- clang-tools-extra/clang-tidy/readability/FunctionCognitiveComplexityCheck.cpp
+++ clang-tools-extra/clang-tidy/readability/FunctionCognitiveComplexityCheck.cpp
@@ -213,6 +213,9 @@
: public RecursiveASTVisitor<FunctionASTVisitor> {
using Base = RecursiveASTVisitor<FunctionASTVisitor>;
+ // If set to true, macros are ignored during analysis.
+ const bool IgnoreMacros;
+
// The current nesting level (increased by Criteria::IncrementNesting).
unsigned short CurrentNestingLevel = 0;
@@ -223,6 +226,9 @@
std::stack<OBO, SmallVector<OBO, 4>> BinaryOperatorsStack;
public:
+ explicit FunctionASTVisitor(const bool IgnoreMacros)
+ : IgnoreMacros(IgnoreMacros){};
+
bool traverseStmtWithIncreasedNestingLevel(Stmt *Node) {
++CurrentNestingLevel;
bool ShouldContinue = Base::TraverseStmt(Node);
@@ -364,6 +370,9 @@
if (!Node)
return Base::TraverseStmt(Node);
+ if (IgnoreMacros && Node->getBeginLoc().isMacroID())
+ return true;
+
// Three following switch()'es have huge duplication, but it is better to
// keep them separate, to simplify comparing them with the Specification.
@@ -493,12 +502,14 @@
StringRef Name, ClangTidyContext *Context)
: ClangTidyCheck(Name, Context),
Threshold(Options.get("Threshold", CognitiveComplexity::DefaultLimit)),
- DescribeBasicIncrements(Options.get("DescribeBasicIncrements", true)) {}
+ DescribeBasicIncrements(Options.get("DescribeBasicIncrements", true)),
+ IgnoreMacros(Options.get("IgnoreMacros", false)) {}
void FunctionCognitiveComplexityCheck::storeOptions(
ClangTidyOptions::OptionMap &Opts) {
Options.store(Opts, "Threshold", Threshold);
Options.store(Opts, "DescribeBasicIncrements", DescribeBasicIncrements);
+ Options.store(Opts, "IgnoreMacros", IgnoreMacros);
}
void FunctionCognitiveComplexityCheck::registerMatchers(MatchFinder *Finder) {
@@ -513,7 +524,7 @@
void FunctionCognitiveComplexityCheck::check(
const MatchFinder::MatchResult &Result) {
- FunctionASTVisitor Visitor;
+ FunctionASTVisitor Visitor(IgnoreMacros);
SourceLocation Loc;
const auto *TheDecl = Result.Nodes.getNodeAs<FunctionDecl>("func");
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