Typedef mismatch

Mismatch between typedef statements

Description

This checker is deactivated in a default Polyspace^® as You Code™ analysis. See Checkers Deactivated in Polyspace as You Code Analysis (Polyspace as You Code).

This defect occurs when typedef statements lead to conflicting underlying types for one of these data types:

• size_t

• ssize_t

• wchar_t

• ptrdiff_t

Risk

If you change the underlying type of size_t, ssize_t, wchar_t, or ptrdiff_t, you have inconsistent definitions of the same type. Compilation units with different include paths can potentially use different-sized types causing conflicts in your program.

For example, say that you define a function in one compilation unit that redefines size_t as unsigned long. But in another compilation unit that uses the size_t definition from <stddef.h>, you use the same function as an extern declaration. Your program will encounter a mismatch between the function declaration and function definition.

Fix

Use consistent type definitions. For example:

• Remove custom type definitions for these fundamental types. Only use system definitions.

• Use the same size for all compilation units. Move your typedef to a shared header file.

Examples

Two Definitions of size_t

file1.c:

        #include <stddef.h>

void func1()
{
    size_t var = 0;
    /*... more code ... */
}

file2.c:

        typedef unsigned char size_t;

void func2()
{
    size_t var = 0;
    /*... more code ... */
}

In this example, Polyspace flags the definition of size_t in file2.c as a defect. This definition is a typedef mismatch because another file in your project, file1.c, includes stddef.h, which defines size_t as unsigned long.

Correction — Use System Definition

One possible correction is to use the system definition of size_t in stddef.h to avoid conflicting type definitions.

file1.c:

          #include <stddef.h>

void func1()
{
    size_t var = 0;
    /*... more code ... */
}

file2.c:

          #include <stddef.h>

void func2()
{
    size_t var = 0;
    /*... more code ... */
}

Correction — Use Shared Header File

One possible correction is to use a shared header file to store your type definition that gets included in both files.

types.h:

          typedef unsigned char size_t;

file1.c:

          #include "types.h"

void func1()
{
    size_t var = 0;
    /*... more code ... */
}

file2.c:

          #include "types.h"

void func2()
{
    size_t var = 0;
    /*... more code ... */
}

Result Information

Group: Programming

Language: C | C++

Default: On

Command-Line Syntax: TYPEDEF_MISMATCH

Impact: High

PQL Name: std.defects.TYPEDEF_MISMATCH

Version History

Introduced in R2016b