How to solve C++ syntax error: 'expected initializer before '=' token'?

How to solve C syntax error: 'expected initializer before '=' token'?

Introduction:
When programming in C, we often encounter various syntax errors. One of the common errors is 'expected initializer before '=' token'. This error is usually caused by a lack of proper initialization in the variable declaration or definition. This article explains the cause of this error and provides several workarounds and sample code.

Error reason:
C When declaring or defining a variable, we are required to use the equal sign '=' after the variable name for initialization. If we forget to add the equal sign, or there is a lack of appropriate initialization on the left side of the equal sign, the compiler will not understand it and report an error.

Solution:
To solve the 'expected initializer before '=' token' error, we need to find the location where the error occurs based on the error message and initialize the variable appropriately. The following are several common solutions:

1. Check variable declarations and definitions:
   First, we need to check the variable declarations and definitions in the code to confirm whether they are initialized correctly . Make sure there is a proper variable name before the equal sign and a correct initialization value after the equal sign.

   Sample code 1:

   int a = 0;  // 正确的变量声明和初始化
   int b;     // 错误，缺少初始化

   In the above sample code, variable a is correctly declared and initialized to 0, while variable b is not initialized, which will cause the compiler to report an error.

2. Check the use of variables in the statement:
   If the location pointed out in the error message is not the place where the variable is declared or defined, then we need to check whether the variable has been used before that location statement to confirm whether the variables are correctly declared and initialized.

   Sample code 2:

   int x = 10;
   int y;
   int z = x + y;  // 错误，变量 y 没有初始化

   In the above sample code, the variable y is not initialized when it is used, causing the compiler to report an error.

3. Check conditional statements and loop statements:
   When using conditional statements and loop statements, we need to ensure that the variables involved in the judgment have been declared and initialized correctly. This is because these statements require initialized variables for comparison and calculation.

   Sample code 3:

   int num;
   if (num > 0) {     // 错误，变量 num 没有初始化
       // do something
   }

   In the above sample code, the variable num is not initialized when it is used in the conditional statement, causing the compiler to report an error.

Summary:
In C programming, the 'expected initializer before '=' token' error is often caused by the lack of correct initialization in the variable declaration or definition. To resolve this error, we need to check where the variable is declared and defined and make sure the variable is initialized correctly. You also need to check the use of variables, conditional statements, loop statements, etc. in the statement to ensure that the variables have been declared and initialized. Through the above solutions, we can efficiently fix this common syntax error.

References:

• C Primer 5th Edition, Stanley B. Lippman, Josée Lajoie, and Barbara E. Moo

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