Thanks for the feedback. I'll have to look more in-depth at Xcode specific 
issues.

> Take a look at this approach:
> * https://github.com/ruslo/sugar/wiki/Cross-platform-warning-suppression
I took a look at your repository. It's very sophisticated. The API that I'm 
supporting has global commands for simple, small projects and then a slightly 
more sophisticated set of commands around targets and source files. It's 
supposed to remove the need of knowing compiler specific flags from the user, 
although they can be manually edited in CMake as always.

The choice of flags for the various compilers are different between the two 
APIs. My API merely turns the warnings up without triggering false positives. 
It may miss some useful warnings. For example, my API uses /W4 instead of /Wall 
for MSVC. I've seen /Wall provide some additional useful warnings, but also 
some distracting, informational ones. There are a few users who agree that some 
of the /Wall warnings are more informational at 
http://stackoverflow.com/questions/4001736/whats-up-with-the-thousands-of-warnings-in-standard-headers-in-msvc-wall.
 Also, I should probably include -Wextra for the GCC warnings like yours does.

From: Ruslan Baratov [mailto:ruslan_bara...@yahoo.com]
Sent: Sunday, March 27, 2016 4:17 PM
To: Geoffrey Viola <geoffrey.vi...@asirobots.com>
Cc: cmake-developers@cmake.org
Subject: Re: [cmake-developers] CMake API for warnings

I like an effort but not an implementation:
* It would be nice to not to set flags globally since we have more fine control 
options like target_compile_options (i.e. different target may have different 
warning settings)
* this will not work for Xcode since warnings should be set by 
XCODE_ATTRIBUTE_* properties

Take a look at this approach:
* https://github.com/ruslo/sugar/wiki/Cross-platform-warning-suppression

Though I think it should be simplified. Best implementation I see so far:
* Remove `RESULT_PROPERTIES`:  implement warning flags -> XCODE_ATTRIBUTE_* 
mapping in CMake itself
* Remove `CLEAR_GLOBAL` option: add user variable checking to CMake so it will 
not set `/W3` (or any other warning flags) by default. May be introduce new 
policy (?)

Ruslo

On 27-Mar-16 12:10, Geoffrey Viola wrote:
CMake should support an API to manage compiler warnings to simplify a common 
problem. Using more compilers with high levels of warnings means cheap static 
analysis and better conformance to standard C++.

Compiler warnings are an easy way to increase program reliability. A use case 
would be to increase compilation warnings on all internal code, ignore warnings 
on all 3rd party code, and treat all warnings as errors.

Attached is an initial attempt to control warnings in CMake. The API has a 
short name (e.g. set_warnings_as_errors) for simplicity and a more technical 
name (e.g. set_warnings_as_errors_folder) to specify scope. Note that the short 
name acts on CMake's folder scope and is meant to be global. The current 
compilers considered are GCC, clang, Green Hills, and MSVC. A CMake Warning is 
issued if the macro does not support a specific compiler so that conformance 
can be guaranteed.

Thanks,
Geoffrey Viola
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