GCC

#pragma GCC diagnostic [action] [warning-name]

#pragma: Directive for the compiler
GCC diagnostic: Indicates a diagnostic command specific to GCC
action: What to do: ignored, warning, or error
warning-name: The name of the warning, e.g. -Wunused-variable, -Wreturn-type, etc.

The function broken_function has a return type of int, but it does not contain a return statement.
This means the function doesn't return a value, even though its declared return type requires one — which violates the function's contract.

main.c


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#include <stdio.h>

int broken_function() {
    // warning: no return statement in function returning non-void [-Wreturn-type]
}

int main() {
    int result = broken_function();
    printf("Result: %d\n", result);
    return 0;
}

The directive #pragma GCC diagnostic error "-Wreturn-type" changes the compiler's behavior so that a warning about a missing return statement in a function with return type int is treated as a compilation error instead of just a warning.

main.c


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#include <stdio.h>

#pragma GCC diagnostic push
#pragma GCC diagnostic error "-Wreturn-type"
int broken_function() {
    //  error: no return statement in function returning non-void [-Werror=return-type]
}
#pragma GCC diagnostic pop

int main() {
    int result = broken_function();
    printf("Result: %d\n", result);
    return 0;
}

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Sektion 4. Kapitel 3

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Kursusindhold

C Preprocessing

1. Introduction to Preprocessing

Introduction to Compilation Stages Role of the Preprocessor Preprocessing Commands

2. Macros

Symbolic Constant Macro With Arguments Advanced Usage of Symbolic Constant Cancel Macro Stringify Operators

3. Conditional compilation

Fundamentals of Conditional Compilation Core Directives Practical Use Cases Pitfalls and Best Practices

4. Compiler Directives and Advanced Control

Communicating with the Compiler Pack GCC Other Built-in Macros Every C Programmer Should Know Precise Control for Debugging and Code Generation

GCC

#pragma GCC diagnostic [action] [warning-name]

#pragma: Directive for the compiler
GCC diagnostic: Indicates a diagnostic command specific to GCC
action: What to do: ignored, warning, or error
warning-name: The name of the warning, e.g. -Wunused-variable, -Wreturn-type, etc.

main.c


              1234567891011
            
#include <stdio.h>

int broken_function() {
    // warning: no return statement in function returning non-void [-Wreturn-type]
}

int main() {
    int result = broken_function();
    printf("Result: %d\n", result);
    return 0;
}

main.c


              1234567891011121314
            
#include <stdio.h>

#pragma GCC diagnostic push
#pragma GCC diagnostic error "-Wreturn-type"
int broken_function() {
    //  error: no return statement in function returning non-void [-Werror=return-type]
}
#pragma GCC diagnostic pop

int main() {
    int result = broken_function();
    printf("Result: %d\n", result);
    return 0;
}

Var alt klart?

Tak for dine kommentarer!

Sektion 4. Kapitel 3