false negative: dangling reference in class

[kidkat]

Based on an issue I might have introduced in ​https://github.com/danmar/simplecpp/pull/254-

#include <string>
#include <vector>

class A {
public:
    A(std::vector<std::string> &filenames);
private:
    std::vector<std::string> &files;
};

A::A(std::vector<std::string> &filenames)
: files(filenames) {}

A make()
{
    std::vector<std::string> files;
    return A(files);
}

##file input.cpp
4: class A {
5: public:
6: A ( std :: vector < std :: string > & filenames@var1 ) ;
7: private:
8: std :: vector < std :: string > & files@var2 ;
9: } ;
10:
11: A :: A ( std :: vector < std :: string > & filenames@var3 )
12: : files@var2 ( filenames@var3 ) { }
13:
14: A make ( )
15: {
16: std ::@expr5 vector < std ::@expr6 string > files@var4 ;
17: return A (@expr7 files@var4 ) ;
18: }



##Value flow
Line 17
  files always size=0

The actual code did not see the implementation of the constructor so that case seems impossible to be detected. If we do see the code we might be able detect this.

[pfultz2]

Fixed by: ​https://github.com/danmar/cppcheck/pull/4024

[kidkat]

This also fixes the inconclusive version I ran into in the same PR:

#include <string>

struct A {
    A(std::string &s);
};

static A f()
{
    std::string s;
    return A(s);
}

input.cpp:10:13: error: inconclusive: Returning object that points to local variable 's' that will be invalid when returning. [returnDanglingLifetime]
    return A(s);
            ^
input.cpp:10:14: note: Passed to constructor of 'A'.
    return A(s);
             ^
input.cpp:9:17: note: Variable created here.
    std::string s;
                ^
input.cpp:10:13: note: Returning object that points to local variable 's' that will be invalid when returning.
    return A(s);
            ^