INFO: C2106 Error Assigning a String Literal to a char Array

• Microsoft C for MS-DOS, versions 6.0, 6.0a, 6.0ax
• Microsoft C/C++ for MS-DOS, version 7.0
• Microsoft Visual C++ for Windows, versions 1.0, 1.5
• Microsoft Visual C++ 32-bit Edition, versions 1.0, 2.0, 2.1, 4.0, 5.0

SUMMARY

A common programming error in C involves an attempt to fill a character array, declared as "char arrayname[somelength]," with a string constant by using the simple-assignment operator (the equal sign, "="). This attempt fails and the compiler generates the following message:

   error C2106: '=' : left operand must be lvalue

   char string1[10] = "String1";
   char *string2 = "String2";

MORE INFORMATION

The following code example does not compile correctly and produces the C2106 error.

Sample Code

   /*
    * Compile options needed: None
    */

   #include <string.h>
   char string1[10];

   void main(void);
   void main(void)
   {
      string1 = "String1";
   }

Sample Code

   /*
    * Compile options needed: None
    */

   /* This example demonstrates some string usage principles. */
   #include <stdio.h>
   #include <string.h>
   #include <malloc.h>

   char string1[40];       /* string1 is an array of char  */
   char *string2;          /* string2 is a pointer to char */
           /* Important: Know when to malloc space for string2. */

   void main(void);
   void main(void)
   {
      /* This shows the correct way to achieve the   */
      /* assignment intended by string1 = "String1"; */
      strcpy(string1, "Contents of string1");
      printf("1:%s\n\n", string1);

      /* These two assignments show two ways to     */
      /* use a char pointer with a string literal.  */
      string2 = "Contents of string2"; /* point to the literal */
      printf("2:%s\n", string2);

      /* allocate memory for char *string2 to point at */
      string2 = (char *)malloc(sizeof(string1));
      strcpy(string2, "Contents of string2, again");
      printf("3:%s\n\n", string2);
      free(string2);

      /* This shows a failed attempt to fill a char  */
      /* array by assignment through a char pointer. */
      string2 = string1;
      string2 = "Contents of string2, but not string1";
      printf("4:%s\n", string1);
      printf("5:%s\n\n", string2);

      /* This shows how correctly to use a pointer   */
      /* to fill a char array with a string literal. */
      string2 = string1;
      strcpy(string2, "Contents of string2, and also string1");
      printf("6:%s\n", string1);
      printf("7:%s\n\n", string2);
   }

   1:Contents of string1

   2:Contents of string2

   3:Contents of string2, again

   4:Contents of string1
   5:Contents of string2, but not string1

   6:Contents of string2, and also string1
   7:Contents of string2, and also string1

Keywords          : CLngIss kberrmsg kbfasttip
Version           : MS-DOS:6.0,6.00a,6.00ax,7.0; WINDOWS:1.0,1.5; WINDOWS  NT:1.0,2.0,2.1,4.0,5.0
Platform          : MS-DOS NT WINDOWS
Issue type        : kbinfo