_Bool Type ¶The C99 standard added _Bool as a C language keyword naming the
boolean type. As an extension, GNU C also recognizes _Bool in
C90 mode as well as with -std=c99 and later.
C23 added bool as the preferred name of the boolean type, but
_Bool also remains a standard keyword in the language and is
supported as such by GCC with -std=c23.
GNU C++ does not support _Bool as a keyword, but including
<stdbool.h> defines it as a macro in terms of standard C++’s
bool type.