Shows the given error message and renders the program ill-formed, or shows the given warning message without affecting the validity of the program(since C++23).
[edit] Syntax#error diagnostic-message (1) #warning diagnostic-message (2) (since C++23) [edit] Explanation
1) After encountering the #error directive, an implementation displays the message diagnostic-message and renders the program ill-formed (the compilation stops).
2) Same as (1), except the validity of the program is not affected and the compilation continues.
diagnostic-message can consist of several words not necessarily in quotes.
[edit] NotesBefore its standardization in C++23, #warning has been provided by many compilers in all modes as a conforming extension.
[edit] Example#if __STDC_HOSTED__ != 1
# error "Not a hosted implementation"
#endif
#if __cplusplus >= 202302L
# warning "Using #warning as a standard feature"
#endif
#include <iostream>
int main()
{
std::cout << "The implementation used is hosted\n";
}
Possible output:
The implementation used is hosted[edit] References
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