I installed Intel Compiler composer_xe_2013_sp1.3.174 on Linux. I am confused about the icc warnings. Feed icc with a simple program main.c as below:
int main(int argc, char **argv) {
int a = 1;
unsigned int b = -22;
if (b = a) {
}
}
I compiled the file with the command: icc -Wall main.c
. Surprisingly, the command works silently without any warnings. Do I have to turn on the warnings switch on icc? Thanks
Generally speaking, the best compilation options for a small program your developing is -Wall -Wextra -std=c11 -pedantic
Contrary to the warning switch's name, Wall does not actually activate all warnings; you use both Wall and Wextra to get the majority of the important warnings.
-std switch sets the standard that the code uses; the most recent one is C11 therefore std=c11. Pedantic is a way to signal to the compiler that you want to write a program that doesn't use compiler-specific extensions. Pedantic requires the std switch and will emit warnings for any syntax, ect. that does not conform to the standard specified by std. Finally, if you want errors instead of warnings for usage of compiler-extension, use -pedantic-errors instead.*
(* - pedantic does not warn about the usage of non-standard libraries like conio.h)
Now if you compile the program with Wall Wextra std=c11 pedantic, you should get 1 warnings:
Warning: Line 4 - Suggest Parenthesis around truthy value (9 out of 10, this means you used = instead == in a comparison context).
If you fix that warning, you'll receive another warning: Warning: Line 4 - Comparison between Signed and Unsigned Integer without a cast.
Adding an explicit cast or changing b to a normal int will solve this warning.