struct as parameter causing "mismatch in formal parameter list"

Question

Hi I'm having a problem using a struct as a parameter.

My struct looks the following:

typedef struct temps {
    string name;
    float max;
} temps;

I can use it in my main without problems like:

temps t;
t.max = 1.0;

but using it in a function signatures like this:

void printTemps(const temps& t) {
    cout << t.name << endl << "MAX: " << t.max << endl;
}

It gives me the following compiler message:

error C2563: mismatch in formal parameter list

Here is a mwe:

#include <iostream>
#include <fstream>
#include <string>
#include <windows.h>
#include <Lmcons.h>

using namespace std;

typedef struct temps {
    string name;
    float max;
} temps;

void printTemps(const temps& t) {
    cout << t.name << endl << "MAX: " << t.max << endl;
}

int main(int argc, char **argv)
{
    temps t;
    t.max = 1.0;
    printTemps(t);
}

Any ideas whats wrong on the struct?

Don't use typedef struct in C++. Show the compiler error message. — , Jul 18 '17 at 21:40
Which headers and using statements did you use? Please post a full [mcve]. — wally, Jul 18 '17 at 21:40
I put `#include` and `using namespace std;` at the top and it compiled fine on g++ 6.3.0 — Luke, Jul 18 '17 at 21:43
Included string and fstream, works fine on Ubuntu 17.04, no warnings or errors even with -Wall. Can't test with windows headers. — Luke, Jul 18 '17 at 21:49
@user2798895 does MCVE you posted compile without windows.h and Lmcons.h? — Luke, Jul 18 '17 at 21:50
Is there a max() macro still in the windows headers? I am thinking of this: https://stackoverflow.com/questions/11544073/how-do-i-deal-with-the-max-macro-in-windows-h-colliding-with-max-in-std — drescherjm, Jul 18 '17 at 22:26
@drescherjm using the name of a function-like macro without `(` following it, does not invoke the macro — M.M, Jul 19 '17 at 00:29

score -1 · Answer 1 · answered Jul 19 '17 at 00:02

You're using the C typedef struct declaration.

typedef struct temps {
    string name;
    float max;
} temps;

//void printTemps(const temps& t) {
void printTemps(const struct temps& t) {  // should match the C idiom
    cout << t.name << endl << "MAX: " << t.max << endl;
}

But since you are programming in C++, you should use the C++ way of declaring structs.

struct temps {
    string name;
    float max;
};

void printTemps(const temps& t) {
    cout << t.name << '\n' << "MAX: " << t.max << '\n';  // using \n is more efficient
}                                                        // since std::endl 
                                                         // flushes the stream

It's true that OP should avoid the typedef, however the typedef makes no change to the program (and therefore this change wouldn't fix the problem, unless the compiler is bugged or OP has not posted the real code, which is probably the case). — M.M, Jul 19 '17 at 00:28

struct as parameter causing "mismatch in formal parameter list"

1 Answers1