Solve the "error: expected declaration before '}' token" problem in C++ code

Solve the "error: expected declaration before '}' token" problem in C code

In the process of writing C code, we often encounter various problems. Various compilation errors. One of the common errors is "error: expected declaration before '}' token". This error usually occurs when there is a pair of braces ({}) in our code that are not matched correctly. This article will explain the causes of this error and provide some ways to resolve it.

Cause Analysis

When the compiler encounters the "expected declaration before '}' token" error when compiling our code, it means that it found an invalid brace in the code . This may be due to several reasons:

1. Missing semicolon: A missing semicolon (;) at the end of the code block can cause this error. For example:

void foo() {
    int x = 2;
    int y = 3
} // 缺少分号

2. Brackets are not matched correctly: In a block of code between a pair of braces, if the braces are not matched correctly, the compiler will think that we are missing a declaration statement. For example:

void bar() {
    if (condition) {
        int x = 2;
} // 括号未正确匹配

3. Quotation marks not paired correctly: If we use quotation marks in a string or character constant, but the quotation marks are not paired correctly, this may also cause the compiler to report an error. For example:

void baz() {
    string s = "Hello world!";
    char c = 'a;
} // 引号未正确配对

Solution

When we encounter the "error: expected declaration before '}' token" error, we can solve the problem based on the cause of the error. Here are some common solutions:

1. Check for missing semicolon: If the error is caused by missing semicolon, we only need to add a semicolon in the corresponding position. For example:

void foo() {
    int x = 2;
    int y = 3;
} // 添加分号

2. Check bracket matching: When encountering a situation where brackets are not matched correctly, we need to carefully check whether the braces in the code block are matched correctly. If there is no match, we need to adjust the position of the brackets according to the logic of the code. For example:

void bar() {
    if (condition) {
        int x = 2;
    } // 正确
} 

3. Check quote pairing: If the error is caused by quotes not being paired correctly, we need to double check the pairing of quotes to make sure each quote has the correct closing quote. For example:

void baz() {
    string s = "Hello world!";
    char c = 'a';
} // 引号正确配对

In addition to the above solutions, we can also use some debugging techniques to help us find the cause of the error. For example, we can use the debugging tools provided by the compiler to step through the program to find the specific location of the problem.

Summary

The "error: expected declaration before '}' token" error is a common compilation error in C code. When we encounter this error, we need to carefully check the code to find out the problem and solve it according to the cause. This article introduces the causes and common solutions to this error, and provides code examples to help readers better understand and solve this problem. I hope that readers can better deal with this common compilation error through the introduction of this article.

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