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gcc -Wall option flag

gcc -Wall enables all compiler's warning messages. This option should always be used, in order to generate better code.

Syntax

$ gcc -Wall [options] [source files] [object files] [-o output file]

Example

Write source file myfile.c:

// myfile.c
#include <stdio.h>

int main()
{
    printf("Program run!\n");
    int i=10;
}

 

Regular build of myfile.c gives no messages:

$ gcc myfile.c -o myfile
$

 

Build of myfile.c with -Wall:

$ gcc -Wall myfile.c -o myfile
myfile.c In function 'main':
myfile.c:6:6: warning: unused variable 'i'
myfile.c:7:1: warning: control reaches end of non-void function
$

 

 

 

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See also

• gcc
• gcc -c
• gcc -D
• gcc -g
• gcc -I
• gcc -L -l
• gcc -o
• gcc -O

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