Why name-mangling has no effect on main function in C++?
C++ compiler often mangle function names to support many features. Programer can suppress default name-mangling using extern "C" way. However, why int main(int, char **) not affected ever?
// test.cpp
int max(int a, int b) {
return a > b ? a : b;
}
extern "C" {
int min(int a, int b) {
return a < b ? a : b;
}
}
int main (int argc, char *argv) {
return 0;
}
And
$ xcrun --sdk macosx clang -x c++ -c test.cpp -o test
$ xcrun nm -nm test
0000000000000000 (__TEXT,__text) external __Z3maxii
0000000000000030 (__TEXT,__text) external _min
0000000000000060 (__TEXT,__text) external _main
Obviously, int max(int, int) is mangled to __Z3maxii; int min(int int) is free from mangling with extern "C" annotation.
How does main escape from mangling?
Is there any way else to keep name from mangling except the above annotation?
c++ main name-mangling
edited Nov 20 at 13:05
YSC
20.4k34594
asked Nov 20 at 13:02
Hans Allen
163
|
show 2 more comments
C++ compiler often mangle function names to support many features. Programer can suppress default name-mangling using extern "C" way. However, why int main(int, char **) not affected ever?
// test.cpp
int max(int a, int b) {
return a > b ? a : b;
}
extern "C" {
int min(int a, int b) {
return a < b ? a : b;
}
}
int main (int argc, char *argv) {
return 0;
}
And
$ xcrun --sdk macosx clang -x c++ -c test.cpp -o test
$ xcrun nm -nm test
0000000000000000 (__TEXT,__text) external __Z3maxii
0000000000000030 (__TEXT,__text) external _min
0000000000000060 (__TEXT,__text) external _main
Obviously, int max(int, int) is mangled to __Z3maxii; int min(int int) is free from mangling with extern "C" annotation.
How does main escape from mangling?
Is there any way else to keep name from mangling except the above annotation?
c++ main name-mangling
edited Nov 20 at 13:05
YSC
20.4k34594
asked Nov 20 at 13:02
Hans Allen
163
1
Is it inconceivable that the compiler makes an exception for this one?
– The Quantum Physicist
Nov 20 at 13:02
1
There's no need to manglemain: it is UB to define anything with the namemainunless it isint main()xorint main(int, char**).
– YSC
Nov 20 at 13:03
out of curiosity: why do you care?
– user463035818
Nov 20 at 13:10
Saymaindoesn't have to explicitly return anything, and nobody cares. Don't mangle its name, and people start losing their mind :)
– StoryTeller
Nov 20 at 13:15
Not much. Just curious. @user463035818
– Hans Allen
Nov 20 at 13:19
|
show 2 more comments
C++ compiler often mangle function names to support many features. Programer can suppress default name-mangling using extern "C" way. However, why int main(int, char **) not affected ever?
// test.cpp
int max(int a, int b) {
return a > b ? a : b;
}
extern "C" {
int min(int a, int b) {
return a < b ? a : b;
}
}
int main (int argc, char *argv) {
return 0;
}
And
$ xcrun --sdk macosx clang -x c++ -c test.cpp -o test
$ xcrun nm -nm test
0000000000000000 (__TEXT,__text) external __Z3maxii
0000000000000030 (__TEXT,__text) external _min
0000000000000060 (__TEXT,__text) external _main
Obviously, int max(int, int) is mangled to __Z3maxii; int min(int int) is free from mangling with extern "C" annotation.
How does main escape from mangling?
Is there any way else to keep name from mangling except the above annotation?
c++ main name-mangling
edited Nov 20 at 13:05
YSC
20.4k34594
asked Nov 20 at 13:02
Hans Allen
163
C++ compiler often mangle function names to support many features. Programer can suppress default name-mangling using extern "C" way. However, why int main(int, char **) not affected ever?
// test.cpp
int max(int a, int b) {
return a > b ? a : b;
}
extern "C" {
int min(int a, int b) {
return a < b ? a : b;
}
}
int main (int argc, char *argv) {
return 0;
}
And
$ xcrun --sdk macosx clang -x c++ -c test.cpp -o test
$ xcrun nm -nm test
0000000000000000 (__TEXT,__text) external __Z3maxii
0000000000000030 (__TEXT,__text) external _min
0000000000000060 (__TEXT,__text) external _main
Obviously, int max(int, int) is mangled to __Z3maxii; int min(int int) is free from mangling with extern "C" annotation.
How does main escape from mangling?
Is there any way else to keep name from mangling except the above annotation?
c++ main name-mangling
c++ main name-mangling
edited Nov 20 at 13:05
YSC
20.4k34594
asked Nov 20 at 13:02
Hans Allen
163
edited Nov 20 at 13:05
YSC
20.4k34594
asked Nov 20 at 13:02
Hans Allen
163
edited Nov 20 at 13:05
YSC
20.4k34594
edited Nov 20 at 13:05
YSC
20.4k34594
edited Nov 20 at 13:05
YSC
20.4k34594
20.4k34594
asked Nov 20 at 13:02
Hans Allen
163
asked Nov 20 at 13:02
Hans Allen
163
asked Nov 20 at 13:02
Hans Allen
163
163
1
Is it inconceivable that the compiler makes an exception for this one?
– The Quantum Physicist
Nov 20 at 13:02
1
There's no need to manglemain: it is UB to define anything with the namemainunless it isint main()xorint main(int, char**).
– YSC
Nov 20 at 13:03
out of curiosity: why do you care?
– user463035818
Nov 20 at 13:10
Saymaindoesn't have to explicitly return anything, and nobody cares. Don't mangle its name, and people start losing their mind :)
– StoryTeller
Nov 20 at 13:15
Not much. Just curious. @user463035818
– Hans Allen
Nov 20 at 13:19
|
show 2 more comments
1
Is it inconceivable that the compiler makes an exception for this one?
– The Quantum Physicist
Nov 20 at 13:02
1
There's no need to manglemain: it is UB to define anything with the namemainunless it isint main()xorint main(int, char**).
– YSC
Nov 20 at 13:03
out of curiosity: why do you care?
– user463035818
Nov 20 at 13:10
Saymaindoesn't have to explicitly return anything, and nobody cares. Don't mangle its name, and people start losing their mind :)
– StoryTeller
Nov 20 at 13:15
Not much. Just curious. @user463035818
– Hans Allen
Nov 20 at 13:19
1
1
Is it inconceivable that the compiler makes an exception for this one?
– The Quantum Physicist
Nov 20 at 13:02
Is it inconceivable that the compiler makes an exception for this one?
– The Quantum Physicist
Nov 20 at 13:02
1
1
There's no need to mangle
main: it is UB to define anything with the name main unless it is int main() xor int main(int, char**).– YSC
Nov 20 at 13:03
There's no need to mangle
main: it is UB to define anything with the name main unless it is int main() xor int main(int, char**).– YSC
Nov 20 at 13:03
out of curiosity: why do you care?
– user463035818
Nov 20 at 13:10
out of curiosity: why do you care?
– user463035818
Nov 20 at 13:10
Say
main doesn't have to explicitly return anything, and nobody cares. Don't mangle its name, and people start losing their mind :)– StoryTeller
Nov 20 at 13:15
Say
main doesn't have to explicitly return anything, and nobody cares. Don't mangle its name, and people start losing their mind :)– StoryTeller
Nov 20 at 13:15
Not much. Just curious. @user463035818
– Hans Allen
Nov 20 at 13:19
Not much. Just curious. @user463035818
– Hans Allen
Nov 20 at 13:19
|
show 2 more comments
2 Answers
2
active
oldest
votes
Per [basic.start.main]/1, [basic.start.main]/2 and [over]/1:
A program shall contain a global function called
main. [...] This function shall not be overloaded. [...] When two or more different declarations are specified for a single name in the same scope, that name is said to be overloaded [...].
This is then undefined behavior to have anything in the global namespace with the name main. There is then no reason for an implementation to mangle main or even consider it to be a proper function.
answered Nov 20 at 13:11
YSC
20.4k34594
add a comment |
Name mangling is a process used by C++ compilers to give each function in your program a unique name. In C++, generally programs have at-least a few functions with the same name ie function overloading, however Main is special, its actually a global function of the C language that can never be overloaded, so it is not necessary.
Take a look at https://en.cppreference.com/w/cpp/language/main_function
And questions about name mangling in C++
(Main) special properties
It cannot be predefined and cannot be overloaded: effectively, the name main in the global namespace is reserved for functions (although it can be used to name classes, namespaces, enumerations, and any entity in a non-global namespace, except that a function called "main" cannot be declared with C language linkage in any namespace (since C++17))
answered Nov 20 at 13:12
RyanN1220
788
add a comment |
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2 Answers
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active
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Per [basic.start.main]/1, [basic.start.main]/2 and [over]/1:
A program shall contain a global function called
main. [...] This function shall not be overloaded. [...] When two or more different declarations are specified for a single name in the same scope, that name is said to be overloaded [...].
This is then undefined behavior to have anything in the global namespace with the name main. There is then no reason for an implementation to mangle main or even consider it to be a proper function.
answered Nov 20 at 13:11
YSC
20.4k34594
add a comment |
Per [basic.start.main]/1, [basic.start.main]/2 and [over]/1:
A program shall contain a global function called
main. [...] This function shall not be overloaded. [...] When two or more different declarations are specified for a single name in the same scope, that name is said to be overloaded [...].
This is then undefined behavior to have anything in the global namespace with the name main. There is then no reason for an implementation to mangle main or even consider it to be a proper function.
answered Nov 20 at 13:11
YSC
20.4k34594
add a comment |
Per [basic.start.main]/1, [basic.start.main]/2 and [over]/1:
A program shall contain a global function called
main. [...] This function shall not be overloaded. [...] When two or more different declarations are specified for a single name in the same scope, that name is said to be overloaded [...].
This is then undefined behavior to have anything in the global namespace with the name main. There is then no reason for an implementation to mangle main or even consider it to be a proper function.
answered Nov 20 at 13:11
YSC
20.4k34594
Per [basic.start.main]/1, [basic.start.main]/2 and [over]/1:
A program shall contain a global function called
main. [...] This function shall not be overloaded. [...] When two or more different declarations are specified for a single name in the same scope, that name is said to be overloaded [...].
This is then undefined behavior to have anything in the global namespace with the name main. There is then no reason for an implementation to mangle main or even consider it to be a proper function.
answered Nov 20 at 13:11
YSC
20.4k34594
answered Nov 20 at 13:11
YSC
20.4k34594
answered Nov 20 at 13:11
YSC
20.4k34594
answered Nov 20 at 13:11
YSC
20.4k34594
20.4k34594
add a comment |
add a comment |
Name mangling is a process used by C++ compilers to give each function in your program a unique name. In C++, generally programs have at-least a few functions with the same name ie function overloading, however Main is special, its actually a global function of the C language that can never be overloaded, so it is not necessary.
Take a look at https://en.cppreference.com/w/cpp/language/main_function
And questions about name mangling in C++
(Main) special properties
It cannot be predefined and cannot be overloaded: effectively, the name main in the global namespace is reserved for functions (although it can be used to name classes, namespaces, enumerations, and any entity in a non-global namespace, except that a function called "main" cannot be declared with C language linkage in any namespace (since C++17))
answered Nov 20 at 13:12
RyanN1220
788
add a comment |
Name mangling is a process used by C++ compilers to give each function in your program a unique name. In C++, generally programs have at-least a few functions with the same name ie function overloading, however Main is special, its actually a global function of the C language that can never be overloaded, so it is not necessary.
Take a look at https://en.cppreference.com/w/cpp/language/main_function
And questions about name mangling in C++
(Main) special properties
It cannot be predefined and cannot be overloaded: effectively, the name main in the global namespace is reserved for functions (although it can be used to name classes, namespaces, enumerations, and any entity in a non-global namespace, except that a function called "main" cannot be declared with C language linkage in any namespace (since C++17))
answered Nov 20 at 13:12
RyanN1220
788
add a comment |
Name mangling is a process used by C++ compilers to give each function in your program a unique name. In C++, generally programs have at-least a few functions with the same name ie function overloading, however Main is special, its actually a global function of the C language that can never be overloaded, so it is not necessary.
Take a look at https://en.cppreference.com/w/cpp/language/main_function
And questions about name mangling in C++
(Main) special properties
It cannot be predefined and cannot be overloaded: effectively, the name main in the global namespace is reserved for functions (although it can be used to name classes, namespaces, enumerations, and any entity in a non-global namespace, except that a function called "main" cannot be declared with C language linkage in any namespace (since C++17))
answered Nov 20 at 13:12
RyanN1220
788
Name mangling is a process used by C++ compilers to give each function in your program a unique name. In C++, generally programs have at-least a few functions with the same name ie function overloading, however Main is special, its actually a global function of the C language that can never be overloaded, so it is not necessary.
Take a look at https://en.cppreference.com/w/cpp/language/main_function
And questions about name mangling in C++
(Main) special properties
It cannot be predefined and cannot be overloaded: effectively, the name main in the global namespace is reserved for functions (although it can be used to name classes, namespaces, enumerations, and any entity in a non-global namespace, except that a function called "main" cannot be declared with C language linkage in any namespace (since C++17))
answered Nov 20 at 13:12
RyanN1220
788
edited Nov 20 at 13:14
answered Nov 20 at 13:12
RyanN1220
788
answered Nov 20 at 13:12
RyanN1220
788
answered Nov 20 at 13:12
RyanN1220
788
788
add a comment |
add a comment |
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1
Is it inconceivable that the compiler makes an exception for this one?
– The Quantum Physicist
Nov 20 at 13:02
1
There's no need to mangle
main: it is UB to define anything with the namemainunless it isint main()xorint main(int, char**).– YSC
Nov 20 at 13:03
out of curiosity: why do you care?
– user463035818
Nov 20 at 13:10
Say
maindoesn't have to explicitly return anything, and nobody cares. Don't mangle its name, and people start losing their mind :)– StoryTeller
Nov 20 at 13:15
Not much. Just curious. @user463035818
– Hans Allen
Nov 20 at 13:19