Add warnings control

[opilar]

Resolves #190

[opilar]

Can it be simpler?

[ronnychevalier]

I am not sure using -Wpedantic is a good idea... It rejects (an error not a warning) some programs using non standard features. Since this is by default it will break many crates using gcc-rs since it is not common for C code to strictly follow ISO C standard.

Also, using -Weverything with clang is not necessarily a good idea either. There is some warnings that do not make sense in some programs. It will just spam the output when compiling for no good reason and it will probably get people used to see warnings, thus they will ignore them...

[opilar]

Thank you!

[alexcrichton]

Thanks! Could you be sure to add some tests for this as well?

Also, is it worth having different sets of default warnings for gcc vs clang?

[ronnychevalier]

I think turning warnings into errors only make sense if you are a developer of the crate using gcc-rs (i.e., enabling the warnings as errors only in a "developer mode" or something). Any user of this crate, or any other crate depending on it, could fail during compile time. Some warnings only appear on some architecture. Some people might have a version of the compiler that have a new warning, but not the developers. Hence, if the developers use another architecture or another compiler they will not have any warning, thus no error. But another person might have the error.

I think it would make sense to put some comment on the risk of using this function in your build.rs?

What do you think?

[alexcrichton]

Sounds fine by me!

[alexcrichton]

Thanks!

[gnzlbg]

I'd like to be able to turn off -Wextra only, many projects compile with -Wall just fine, but they don't compile silently with -Wextra, and this is on purpose.

[gnzlbg]

Why was -Wextra added here? -Wextra is basically the set of warnings that aren't good enough to be enabled by default, due to either false-positives, or because they are opinionated. Enabling them for all projects by default, and providing only a way to either use -Wall -Wextra or no warnings at all, does not appear to be reasonable behavior to me.