The most useful GCC options and extensions

#1

Post by antoarts » Mon, Jul 11, 2011, 5:08 PM UTC

The most useful GCC options and extensions
antoarts.com

Re: The most useful GCC options and extensions

#2

Post by matthavener » Mon, Jul 11, 2011, 6:17 PM UTC

A few others I use are -Wsign-compare and -Wformat-nonliteral. Sign compare warns on possible bugs/vulnerabilities due to comparing signed and unsigned values. Using nonliteral formats can lead to vulnerabilities (such as the famous attacks on FTP servers http://seclists.org/bugtraq/1999/Sep/328)

Re: The most useful GCC options and extensions

#3

Post by tedunangst » Mon, Jul 11, 2011, 6:23 PM UTC

I was definitely not expecting an article about useful GCC options to mention -trigraphs. The -ansi option isn't particularly useful either, imo, since just about every interesting program is going to do something crazy like open a network socket or list the files in a directory.

By far the most useful gcc extension wasn't mentioned at all. typeof().

Re: The most useful GCC options and extensions

#4

Post by antoarts » Mon, Jul 11, 2011, 6:30 PM UTC

tedunangst wrote: post #3

I was definitely not expecting an article about useful GCC options to mention -trigraphs. The -ansi option isn't particularly useful either, imo, since just about every interesting program is going to do something crazy like open a network socket or list the files in a directory. By far the most useful gcc extension wasn't mentioned at all. typeof().

I mentioned trigraphs as an example of a C standard feature disabled by default in GCC, and then I just mentioned how to enable just that feature. It wasn't supposed to be included among the most important options, it just got there ;-).

Re: The most useful GCC options and extensions

#5

Post by ryanpetrich » Mon, Jul 11, 2011, 6:46 PM UTC

Another useful GCC extension is statements within expressions:

#define max(a,b) ({ typeof (a) _a = (a); typeof (b) _b = (b); _a > _b ? _a : _b; })

Re: The most useful GCC options and extensions

#6

Post by afhof » Mon, Jul 11, 2011, 6:57 PM UTC

Sometimes when compiling and trying to use system calls gcc will complain about the functions not existing. This is usually because of some preprocessor guard not being defined. An easy way to see what macros have been defined is to run gcc with the "-E -dM" flags.

Re: The most useful GCC options and extensions

#7

Post by gaius » Mon, Jul 11, 2011, 7:09 PM UTC

"If Java had true garbage collection, most programs would delete themselves upon execution." — Robert Sewell

Nice ;-)

Re: The most useful GCC options and extensions

#8

Post by defen » Mon, Jul 11, 2011, 9:43 PM UTC

Computed goto: http://gcc.gnu.org/onlinedocs/gcc-3.4.1/gcc/Labels-as-Values...

Re: The most useful GCC options and extensions

#9

Post by pwpwp » Mon, Jul 11, 2011, 11:03 PM UTC

My favorite is the "weak" attribute. http://gcc.gnu.org/onlinedocs/gcc/Function-Attributes.html

Makes separate compilation for languages that compile to C much easier.

Re: The most useful GCC options and extensions

#10

Post by zokier » Mon, Jul 11, 2011, 11:27 PM UTC

matthavener wrote: post #2

A few others I use are -Wsign-compare and -Wformat-nonliteral. Sign compare warns on possible bugs/vulnerabilities due to comparing signed and unsigned values. Using nonliteral formats can lead to vulnerabilities (such as the famous attacks on FTP servers http://seclists.org/bugtraq/1999/Sep/328 )

-Wall includes -Wsign-compare