Re: [boost] CMake - one more time

Subject: Re: [boost] CMake - one more time
From: Robert Ramey (ramey_at_[hidden])
Date: 2016-04-23 13:08:32

> This is not necessary at all. Cmake provides the `BUILD_SHARED_LIBS` variable that can be set to do this same purpose:
>
> https://cmake.org/cmake/help/v3.5/variable/BUILD_SHARED_LIBS.html

Of course I saw this. This is a great example of the kind of thing that 
drives me nuts. looking at the CMake documentation

a) Its not clear how the variable is supposed got get set in the first 
place.  Is one expected to include in the CMakeLists.txt file a 
statement like
set(BUILD_SHARED_LIBS TRUE)
?
But wouldn't that constraint the build to shared or static library? What 
if you want to choose?

b) What is the default? - oh it might depend upon whether "option()" is 
used somewhere.  Instead of providing an answer it just gives you 
another question.

c) So it is not clear on its face whether the statement 
add_library(target_name ....) builds a static or shared library.  It 
depends upon some other "global" variable.  That is you cannot know
what a statement will do by looking at the statement.  Worse yet,
the behavior of the statement may depend upon some higher level 
CMakeLists.txt file that you might not even be aware of.

d) is BUILD_SHARED_LIBS a cached variable?

I could go on, but you get the idea.  And this is just one single
variable.  There are dozens with similar behavior and implications.
As far as I can tell, all other build systems suffer from the same 
problems.  And the documentation actually makes it worse because it 
suggests that the system is simple to use when it's actually not.  It 
makes naive users feel like they're stupid - whether they are or not.

And this is made worse by the fact that there are lots of people who 
have made simple build scripts for small projects with limited 
requirements.  This work the first time - now they think it IS easy and 
they think there's nothing to it.  It's depressing.

One cannot make a build script without deep trolling of the net to find 
he cause of arbitrary surprises. You can't just read a build script and 
know what it does.

Robert Ramey