Error description

unknown type name ‘bool’

Recently, using C to implement data structure encountered the following error

➜  LinkedList gcc list.c 
list.c:14:1: error: unknown type name ‘bool’; did you mean ‘_Bool’?
 bool is_empty(PNODE pHead);
 ^~~~
 _Bool
list.c:77:1: error: unknown type name ‘bool’; did you mean ‘_Bool’?
 bool is_empty(PNODE pHead)
 ^~~~
 _Bool
list.c: In function ‘is_empty’:
list.c:80:9: error: ‘true’ undeclared (first use in this function); did you mean ‘free’?
  return true;
         ^~~~
         free
list.c:80:9: note: each undeclared identifier is reported only once for each function it appears in
list.c:82:9: error: ‘false’ undeclared (first use in this function); did you mean ‘fclose’?
  return false;
         ^~~~~

Error reason

Unknown type name: ‘bool’, because there is no boolean type defined in the C language standard (C89), an error will be reported. C99 provides a header file & lt; stdbool.h> defines bool , true represents 1 and false represents 0. As long as you import stdpool. H , you can easily operate Boolean types.

#include <stdbool.h>