Thread: The best gcc options? Just everyday use.

So one day I was brainstorming what to research next, and I wanted to know about gcc options to help me with my code for everyday (everycompile) use. So I was reading this thread, and I came across one of Salem's posts:

Code:

$ gcc -W -Wall -ansi -pedantic -O2  hello.c

I thought it was pretty cool, mainly because I didn't know what it was saying. So I decided to:

Code:

man gcc
(this is a way in Linux to call for help files for a specific program)

I found out that
-W is for enabling warnings
-Wall for all warnings
-ansi for strict C semantics
-pedantic required by -ansi
-O2 for pretty good optimizations

So my main question is, is this the preferred way to compile C code for everyday use?

Well -W -Wall is redundant since -Wall covers all warnings.

-ansi turns off certain GCC extentions that aren't ansi. It doesn't turn off certain features and if you use those features the program will still compile ok.

-pedantic will warn / error on the features not turn off by -ansi

as for -O2: I never run the optimization switch until I am done debugging my program. Since the structure of the program can be changed it can make it difficult to debug using a debugger such as gdb.

I use the following for every day programming: -Wall -Werror -ansi -pedantic -g
I use makefiles to control my projects, so I'll sometimes drop the -g and -ansi and -pedantic and put in optimization or some other switches.

-g btw causes the debugging symbols to be included in the executable

Originally Posted by Thantos

I use the following for every day programming: -Wall -Werror -ansi -pedantic -g

Is -Werror redundent since -Wall covers all warnings?

Nope, Werror doesn't turn on any extra warnings. It changes how they are viewed. Normally when you have a warning its just that a warning that you can ignore. Werror tells the compiler to treat warnings as errors. When you compile and recieve an error the compiler will not produce an executable.

I like these options! Except for one thing:
I can't use C++ comments :(
Should I get used to C style comments? I'll try my best :(

To use the // comments you have to:
A) Be programming in C++ (and then use g++)
B) Be programming in C99 in which case you need to add -std=c99

Not unless you specify the -std=c99. Though I haven't tested it with -ansi and -pedantic.

The -O switch has the side-effect of making the "use before initialisation" warnings apparent.

Code:

int a;
if ( a == 0 )  // oops, a not initialised

Read the -Wuninitialized disclaimer in the manual.

> I can't use C++ comments
Well at a push, you could specify
-Wno-comment
which along with all your other -W options turn on all the warnings EXCEPT for that one.

Another alternative is to specify
-std=c99
since C99 allows for // comments
But I'd be a bit wary of using too many new C99 features since there aren't too many compilers which fully support C99.