C++ function debugging explained: How to find the line of code that caused the error?

In C development, function debugging can help identify erroneous lines of code. Debugging is possible by using GDB, the Visual Studio debugger, or assertions. GDB provides powerful command line debugging capabilities, including setting breakpoints, executing line by line, printing variables, etc. The Visual Studio debugger provides a graphical interface that supports breakpoints, stepping, viewing variables, and tracing function calls. Assertions can be checked by the code, and when the condition is not true, the program will be terminated and an error message will be printed. Through these technologies, developers can debug code efficiently, shorten debugging time and improve code quality.

# Detailed explanation of C function debugging: How to find the line of code that caused the error?

In C development, function debugging is crucial to finding the lines of code that cause errors. This article will introduce common function debugging techniques in detail and provide a practical case to demonstrate its application.

1. GDB (GNU Debugger)

GDB is a powerful command-line debugger for analyzing code execution and diagnosing problems. To use GDB, enter the following command in the terminal:

gdb 程序名

You can then debug using the following command:

• break: At the specified line of code Set a breakpoint at.
• run: Run the code until it reaches the breakpoint.
• step: Execute the code line by line.
• next: Skips the function call and continues code execution.
• print: Print the value of a variable or expression.

2. Visual Studio Debugger

Visual Studio IDE has a powerful graphical debugger built-in. In debug mode, the following tools are available:

• Breakpoints: Add breakpoints at lines of code.
• Stepping: Execute code line by line or function by function.
• Local variable window: View local variables in the function.
• Call stack window: Track the sequence of function calls.

3. Assertion

Assertion is a code check. If a certain condition is not true, it will cause the program to terminate and print an error message. For example:

assert(condition == true);

Practical case: finding illegal parameters

Consider the following C function:

int sum(int a, int b) {
  if (a < 0 || b < 0) {
    throw std::invalid_argument("负数参数无效");
  }

  return a + b;
}

If a negative number is passed to this function, ## will be raised #std::invalid_argument Exception.

Debugging with GDB

(gdb) break sum.cpp:10
(gdb) run
(gdb) n
(gdb) print a
(gdb) print b

This will set a breakpoint at line 10 and run the program. After that, execute the code line by line and print the values ​​of

a and b to identify the illegal parameters that caused the exception.

Using the Visual Studio Debugger

In Visual Studio, set a breakpoint at line 10, and then run the program. In the debugger toolbar, you can use the Steps tool to step through the code and examine the

a and b values ​​in the Local Variables window.

Conclusion

Mastering function debugging techniques is crucial to effectively debugging C code. By using GDB, the Visual Studio debugger, or assertions, developers can easily pinpoint the lines of code that cause errors, reducing debugging time and improving code quality.

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