clang/lib/StaticAnalyzer/Checkers/StdLibraryFunctionsChecker.cpp:697: possible performance problem ?

[dcb314]

Static analyser cppcheck says:

trunk/clang/lib/StaticAnalyzer/Checkers/StdLibraryFunctionsChecker.cpp:697:24: performance: Function parameter 'ArgTys' should be passed by const reference. [passedByValue]

Source code is

Signature(ArgTypes ArgTys, RetType RetTy) {

but

using ArgTypes = std::vector<std::optional>;

So it looks to me like an entire vector is put onto the stack.

[llvmbot]

@llvm/issue-subscribers-clang-static-analyzer

Author: None (dcb314)

Static analyser cppcheck says:

trunk/clang/lib/StaticAnalyzer/Checkers/StdLibraryFunctionsChecker.cpp:697:24: performance: Function parameter 'ArgTys' should be passed by const reference. [passedByValue]

Source code is

Signature(ArgTypes ArgTys, RetType RetTy) {

but

using ArgTypes = std::vector<std::optional<QualType>>;

So it looks to me like an entire vector is put onto the stack.

[NagyDonat]

While std::vector objects can be very large, in this particular case the vector stores the types of the arguments of a function from the standard library, so it's known to be small. (Typical standard library functions have 2-3 arguments.)

[steakhal]

Maybe we could use SmallVector for that to also clarify the intent - and/or take them by const reference?

[dcb314]

In the same file, cppcheck reports:

trunk/clang/lib/StaticAnalyzer/Checkers/StdLibraryFunctionsChecker.cpp:1749:44: performance: Function parameter 'Names' should be passed by const reference. [passedByValue]
trunk/clang/lib/StaticAnalyzer/Checkers/StdLibraryFunctionsChecker.cpp:1749:75: performance: Function parameter 'Sum' should be passed by const reference. [passedByValue]

To me, const reference looks to be the suggested improvement.