Warning comparison between pointer and integer

问题

I am getting an error when I iterate through the character pointer and check when the pointer reaches the null terminator.

 const char* message = "hi";

 //I then loop through the message and I get an error in the below if statement.

 if (*message == "\0") {
  ...//do something
 }

The error I am getting is:

warning: comparison between pointer and integer
      ('int' and 'char *')

I thought that the * in front of message dereferences message, so I get the value of where message points to? I do not want to use the library function strcmp by the way.

回答1:

It should be

if (*message == '\0')

In C, simple quotes delimit a single character whereas double quotes are for strings.

回答2:

This: "\0" is a string, not a character. A character uses single quotes, like '\0'.

回答3:

In this line ...

if (*message == "\0") {

... as you can see in the warning ...

warning: comparison between pointer and integer
      ('int' and 'char *')

... you are actually comparing an int with a char *, or more specifically, an int with an address to a char.

To fix this, use one of the following:

if(*message == '\0') ...
if(message[0] == '\0') ...
if(!*message) ...

On a side note, if you'd like to compare strings you should use strcmp or strncmp, found in string.h.

来源：https://stackoverflow.com/questions/32510218/warning-comparison-between-pointer-and-integer