How to solve the problem of the return value of the C language function being ignored?

The return value of C language function is ignored, which will lead to the failure to obtain the execution result and cover up the error. The solutions include: carefully reading the function document, explicitly using the return value, turning on the compiler warning, and using assertions. Develop good programming habits, pay attention to function return values, and write robust and reliable code.

Is the return value of C function ignored? Don't panic, let's talk about this!

Many novices, even some veterans, will encounter this problem: C language functions work hard to calculate the result, but because the caller ignores the return value, the program runs incorrectly and even crashes. It’s like carefully preparing a full table of Manchu and Han banquets, but the guests were just chatting and didn’t even touch a single bite of the dishes. Isn’t that a pity?

In this article, let’s analyze the root cause of this problem and how to avoid it gracefully. After reading it, you will be able to better understand the mechanism of C language functions and write more robust and reliable code.

Let’s start with the basics: What is the return value of the function?

A function, you can understand it as a "black box". You throw some data (parameters) into it, and it spits out a result (return value) after a series of operations. This return value is the embodiment of the function execution result and is crucial! Functions without return values ​​are usually used to perform some side effects, such as modifying global variables, printing information, etc. But for the most part, we need the function to return a meaningful value.

The consequences of the return value being ignored

Ignoring the return value, the most direct consequence is that you cannot get the execution result of the function. It's like you ordered a takeaway and the delivery guy delivered it, but you didn't open the door, and the takeaway would get cold and you didn't eat it. What's more serious is that the return value of some functions is not only the result, but may also contain error codes or status information. Ignoring this information, you may not know what errors occurred during the function operation, which leads to difficult bugs in the program.

How to avoid ignoring the return value?

This is actually very simple, but it requires good programming habits.

• Read function documents carefully: Each function should have clear documentation instructions, including its functions, parameters, return values ​​and possible error codes. Developing the habit of reading documents can help you understand the purpose of a function and how to use its return value correctly.
• Use the return value explicitly: Don't let the return value disappear silently. Even if you don't need to use the return value for the time being, you should explicitly assign it to a variable, or at least print it out with a statement, which can help you discover potential problems.

 <code class="c">#include <stdio.h> #include <stdlib.h> int my_function(int a, int b) { if (b == 0) { fprintf(stderr, "Error: Division by zero!\n"); //报错信息输出到标准错误流return -1; // 返回错误码} return a / b; } int main() { int result = my_function(10, 2); //正确使用返回值if (result == -1) { fprintf(stderr, "Function execution failed!\n"); } else { printf("Result: %d\n", result); } my_function(10, 0); //忽略返回值，程序会输出错误信息，但不会被main函数捕获处理// 更优雅的处理方式，使用一个变量接收返回值int anotherResult = my_function(10,0); if (anotherResult == -1){ //进行错误处理} return 0; }</stdlib.h></stdio.h></code>

In this example, the my_function function returns -1 when the divisor is 0, indicating an error. main function should check this return value and take corresponding measures based on the return value. Ignore the return value. Although the program can run, the result is incorrect and it is easy to cover up the error.

• Compiler Warning: Many compilers provide warning options to detect situations where the return value is ignored. Turn on these warning options to help you spot potential problems during the compilation phase. For example, GCC's -Wall option is a good choice.

Some more advanced tips

For complex programs, consider using assert to check the return value of the function. Assertions can help you detect problems early in the development phase and avoid unexpected situations at runtime.

 <code class="c">#include <assert.h> // ... (前面的代码) ... int main() { int result = my_function(10, 2); assert(result != -1); // 断言返回值不等于错误码printf("Result: %d\n", result); return 0; }</assert.h></code>

Remember, writing high-quality C code is not only to make the program run, but also to make the program robust, reliable and easy to maintain. Paying attention to function return values ​​is an important part of writing high-quality C code. Don’t let your “Manhan Banquet” be done in vain!

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