CS50 - C++: issue with " using namespace std;" [duplicate] - c++

Question

There's a C++ code:
#include <stdio.h>
int main() {
int b = sizeof('a');
if(b==4) printf("I'm a C program!\n");
else printf("I'm a C++ program!\n");
}
Compile it like this:
gcc main.cpp -o main
It succeeds and gives:
I'm a C++ program!
Then add a line somewhere inside function main
int *p1 = new int [1000];
It fails with:
C:\Users\...\AppData\Local\Temp\cccJZ8kN.o:main1.cpp:(.text+0x1f): undefined reference to operator new[](unsigned long long)'
collect2.exe: error: ld returned 1 exit status
Then the following two commands successfully compile the code:
gcc main.cpp -o main -lstdc++
and
g++ main.cpp -o main
The compiler is minGW-win64 (http://mingw-w64.sourceforge.net/).
The questions are:
Which of the two last commands are better?
To my mind gcc correctly chooses the right compiler but then uses a wrong linker. Is it right?
May it be a problem in minGW-win64?
As I see (correct me if it's wrong) gcc was intended to be a main program that takes the input and decides what to do with it. So I'd better use gcc if it worked without -lstdc++. But if it's not possible I'll prefer using g++ instead as don't know what else gcc may miss.
Many thanks for your considerations

Answer 1

gcc is the GCC compiler-driver for C programs, g++ is the one for C++ programs.
Both will guess the language on the basis of the file-extension, unless overridden.
But if you use the wrong driver, the default-options will be wrong, like leaving out the C++ standard-library for C++ programs compiled with gcc when linking.
You can add just the library with -lstdc++, though using the proper driver is preferable, as plain gcc may be missing other, subtler options.