What s wrong with the C program? The prompt uses an undefined type

Which one struct is defined.

I don't think you have a definition.

This means that "incomplete information is not allowed" is usually a struct that you have defined.

For example: struct {.}

int a;

char b;

mystruct;

Then you use this struct to define a variable that looks like this:

mystruct x,y;

This is not allowed in ANSI C (C++ does).

To be written or contained as such:

struct mystruct x,y;

There will be no problem.

A pointer to an array is defined, and since the length of the array is not determined, the compiler says that the structure definition is incomplete, because the length of the array is not determined, and the weight of the unit length of the calculation pointer cannot be calculated. Here's how to fix it:

1. The pointer of the variable is the address of the variable. The variable that holds the address of the variable is a pointer variable. That is, in C, it is allowed to store pointers with a variable, which is called a pointer variable.

2. In order to represent the relationship between the pointer variable and the variable it points to, the "*" symbol is used to represent "point" in the program.

3. Define a pointer variable The definition of a pointer variable includes three contents, wherein, it means that this is a pointer variable, the variable name is the name of the defined pointer variable, and the type specifier represents the data type of the variable pointed to by the pointer variable.

5. Another example: int *s is a pointer variable pointing to an integer variable, and float *d is a pointer variable pointing to a floating-point variable. ，char *g;is a pointer variable that points to a character variable.

This means that the appearance of "incomplete information is not allowed" generally defines a struct.

For example: struct mystruct;

Then when you use this struct to define a variable, you write it like this: mystruct x,y; This is not allowed in ANSI C (C++ does) and is copied like this: struct mystruct x,y, and there is no problem.

In the case of C, the phrase "incomplete information is not allowed" is usually when you define a struct such as struct mystruct;

Then you use this struct to define a variable that looks like this:

mystruct x,y;

This is not allowed in ANSI C (C++ does) and should be written like this:

struct mystruct x,y;

There will be no problem.

It may be that the header file is not included, and this is how I encountered this problem.

Please post the specific error information and which line is wrong.

1. This error should be an external reference to a variable, but the definition of the variable is not found when connecting.

2. References to something that linkers can't find in libraries and object files (such as functions, variables, or tags).

This reason is more complicated, if it is your own problem, please provide a definition for each declaration (including functions, extern variables, etc.), if it is a library problem, it may be that a library is not found, or it may be a difference in the name resolution of C C++ functions.

In C, there are several reasons for the occurrence of undefined:

1. The variable type is not specified.

2. The way of specifying types is confused with C++, especially in the . This kind of error is prone to occur in c files.

3. The variable specifies the type, but it does not match the name of the variable used, and the name of the variable used will prompt that it is undefined.

First of all, your elemtype and ok are not defined, ok a macro or what, what is elemtype, a struct or what?

If ok is a macro to be added, elemtype is a struct in the first line of the source file by adding the following**.

#defineok1

I'm the separator*

typedef

struct

sqlist;

Change the following ** to the following ***

typedef

struct

elemtype

sqlist;;