C 编程语言，如何在代码中转换输入字符串并运行它[暂停]

Question

Is there a way to transform what the user inputs in code? like if

char k[50]; 
printf("insert the code to insert");
scanf("%s", &k);

function => converts string and execute the string if the code is correct

for example if the user insert "int a = 0;" as input, the program run the input string?

Answer 1

What you're looking for is essentially something like the eval function that some languages has.

Nope, there is not a way to do that. At least not in a practical way. The reason is quite simple. In C, you need to compile the complete program before you run it. If there is even a single syntax error in you 10k+ lines of code, you will not get an executable binary from the compiler.

Python on the other hand can execute line by line. That's why you can execute Python code that has syntax errors. The program will not crash until you encounter the error.

Besides, you should always think twice before using something like this irregardless of the language. The risks for vulnerabilities are extremely high.

Answer 2

Contrary to some other languages, the C language doesn't have an eval function to do what you want. The only option is to write the source file into a file and then execute the compiler available on the host machine.