Unable to pass TCHAR as parameter in C/C++ - c++

Question

Here is Minimal example :-
#include <stdio.h>
#include <Windows.h>
using namespace std;
void myFunc(TCHAR Path)
{
printf("pathLen : %lu\n", sizeof(Path));
printf("character size : %lu\n", sizeof(*Path));
printf("pathLenInBytes : %lu\n", sizeof(Path) * sizeof(*Path));
}
int main()
{
TCHAR selfPath[MAX_PATH];
if (GetModuleFileName(NULL, selfPath, MAX_PATH) == 0) // Getting exe File Location
printf("Error : %lu\n", GetLastError());
printf("Self Path : %s\n", selfPath);
myFunc(selfPath);
return 0;
}
Here is Error Output from MinGW-W64 Compiler :-
g++ -Os -s -o goga.exe tesst.cpp
tesst.cpp: In function 'void myFunc(LPCSTR, TCHAR)':
tesst.cpp:9:43: error: invalid type argument of unary '*' (have 'TCHAR' {aka 'char'})
9 | printf("character size : %lu\n", sizeof(*Path));
| ^~~~
tesst.cpp:10:35: error: 'pathLen' was not declared in this scope
10 | printf("pathLenInBytes : %lu\n", pathLen * sizeof(*Path));
| ^~~~~~~
tesst.cpp:10:53: error: invalid type argument of unary '*' (have 'TCHAR' {aka 'char'})
10 | printf("pathLenInBytes : %lu\n", pathLen * sizeof(*Path));
| ^~~~
tesst.cpp: In function 'int main()':
tesst.cpp:23:22: error: invalid conversion from 'TCHAR*' {aka 'char*'} to 'TCHAR' {aka 'char'} [-fpermissive]
23 | myFunc("AppBroker", selfPath);
| ^~~~~~~~
| |
| TCHAR* {aka char*}
tesst.cpp:6:32: note: initializing argument 2 of 'void myFunc(LPCSTR, TCHAR)'
6 | void myFunc(LPCSTR Name, TCHAR Path)
| ~~~~~~^~~~
But If I put the GetModuleFineName() directy inside myFunc() then it works :-
#include <stdio.h>
#include <Windows.h>
using namespace std;
void myFunc()
{
TCHAR selfPath[MAX_PATH];
if (GetModuleFileName(NULL, selfPath, MAX_PATH) == 0) // Getting exe File Location
printf("Error : %lu\n", GetLastError());
printf("Self Path : %s\n", selfPath);
printf("pathLen : %lu\n", sizeof(selfPath));
printf("character size : %lu\n", sizeof(*selfPath));
printf("pathLenInBytes : %lu\n", sizeof(selfPath) * sizeof(*selfPath));
}
int main()
{
myFunc();
return 0;
}
But I dont need it this way. How can i solve this error ?
EDIT : Tried replacing myFunc(TCHAR Path) with myFunc(TCHAR *Path) & also with myFunc(TCHAR Path[]). Both Work and program compiles successfully but the output is different that expected output now !
Expected Output :-
Self Path : C:\Users\username\Desktop\Coding\PETS\muse\goga.exe
pathLen : 260
character size : 1
pathLenInBytes : 260
Output that I Get:-
Self Path : C:\Users\username\Desktop\Coding\PETS\muse\goga.exe
pathLen : 8
character size : 1
pathLenInBytes : 8

Answer 1

I make an attempt to answer
In your first version, your prototype must be
myFunc(TCHAR *Path) or myFunc(TCHAR Path[]) because a path is an array of TCHAR, thus a TCHAR*
(a starting documentation can be found here or here)
What you obtained from the first code that compiles is only what you have asked.
Let us see:
printf("pathLen : %lu\n", sizeof(Path));
printf("character size : %lu\n", sizeof(*Path));
printf("pathLenInBytes : %lu\n", sizeof(Path) * sizeof(*Path));
First remark: you should not use sizeof (thanks # Remy LEABEAU for review) with TCHAR* but _tcslen() or lstrlen
In the first line, you asked to display the size of path which is a pointer (a TCHAR*). The size
of a pointer can be 4 bytes or 8 bytes depending on your system(ref). So 8 is correct.
In an array, its name is also the adress of the first element in it. Thus if you try to printf
sizeof(*Path), you ask to print the size of the first character pointed by the pointer, thus 1.
The two previous lines also explain what the thrid line gives you: 1*8 = 8.
If pathLenis the size in byte of the path, you may use _tcslen() or lstrlen() to compute the length of the path and then use sizeof(TCHAR) as found here
Proposition to obtain what your needed output:
printf("pathLen : %lu\n", _tcslen(Path));
printf("TCHAR size : %lu\n", sizeof(TCHAR));
printf("pathLenInBytes : %lu\n", _tcslen(Path)* sizeof(*Path));