Re: Capabilities of backend compiler and conditional flags

[timothee]

Seems indeed useful to have a standard library module for that.

Could be based on stuff like this :


const output = staticExec("cc --version")`
when output.hasSomeProperty: ... # eg: check version > something


Run


const hasLTO = not staticExec("clang -flto --version").contains("error")
when hasLTO: ...


Run

Capabilities of backend compiler and conditional flags

[arnetheduck]

Increasingly, I've been running into situations where it would be beneficial, 
from a cross-platform and cross-compiler point of view, to selectively enable 
flags and features depending on the capabilities and defaults of the C compiler 
is being used. There is some support for doing stuff like `when gcc`, but it's 
crude.

Let's say for example that a project would benefit from LTO compiles - what's 
the best way to enable this for compilers that support it and gracefully 
degrade to non-LTO? Only recent GCC versions support it.

A similar situation arises with dialects - which one is the default for a given 
compiler (C99, C11, etc) changes over time, while something like a wrapper 
might need to force a particular version for a particular compiler - likewise 
for -arch flags and the like.

Autoconf solves this pragmatically, simply by running tests for each 
interesting feature and spitting out a decision variable that can be used later 
in the build process - what would nim's approach be?

A non-solution is to dump this one the user of the code (ie "go edit your 
nim.cfg") - this doesn't scale.