[CMake] XCODE_DEPEND_HELPER dependency issues

[Bill Hoffman]

Nicolas Tisserand wrote:
> Hi,
> 
> I'm working on a C++ project that's been happily using CMake as a
> cross-platform (mac/pc/linux) build tool for a year now.
> 
> We're using CMake 2.4.6 on all platforms.
> 
> Recently, some changes in our build system lead to the following
> dependency graph:
> 
> LIB1 <- EXE1 <- LIB2 <- EXE2
>   ^                                    |
>    `-----------------------------------'
> 
> (LIB* are static libraries, and EXE* executables)
> 
> EXE1 is a tool that generates input source files for LIB2, hence the
> extra-dependency.
> 
> Everything works nice and smooth with the Linux / Make, MacOS X / Make
> and WIN32 / VC80 generators.
> 
> Trouble is, on the mac, the XCODE_DEPEND_HELPER (XDH) is added to all
> final (executable, dynamic libraries and modules) targets by the XCode
> generator:
> 
>   .---------------------------------------
>   v                                        \
> LIB1 <-------.                          |
>               EXE1 <- LIB2  <- EXE2
> XDH <-------'                           |
>   ^---------------- -----------------------'
> 
> When EXE2 (or ALL_BUILD) is the active target and LIB2 needs a
> rebuild, the following happens:
> 
> * The XCODE_DEPEND_HELPER make command is run, doing nothing.
> * EXE1 is left alone
> * LIB2 gets correctly rebuilt
> * EXE2 does not get relinked because when XCODE_DEPEND_HELPER was run,
> EXE2 was still up-to-date with LIB2 :-(
> 
> This is very annoying.
> 
> Here's the only sort-of workaround I could come up with:
> 
> * remove the EXE1 <- LIB2 dependency, so that EXE2 gets correctly
> relinked when the active target is EXE2
> * exclude EXE1 from the build (using EXCLUDE_FROM_ALL), so that EXE2
> gets correctly relinked when the active target is ALL_BUILD
> 
> But this forces XCode users to rebuild EXE1 manually.
> 
> 
> Finally, here are my questions:
> 
> Is there a nicer solution to my problem?
> Is this a known bug?
> Are there any plans for fixing it?
> Would 2.4.7 solve my problems? (I checked the ChangeLogs but did not
> see any mention of it)
> 
> Sorry for the bad ascii-art :-)

You should create a small example that shows the problem, and attach it 
to a bug report.

-Bill