implementation of configure.env-append

[Blair Zajac]

> On Oct 8, 2019, at 1:59 AM, Ryan Schmidt <ryandesign at macports.org> wrote:
> 
> 
> 
> On Oct 6, 2019, at 14:05, Ken Cunningham wrote:
> 
>> I think I have tried this enough ways to be close, but I just want to be certain.
>> 
>> I want to *append* a value onto an existing environment variable from a Portfile. I don’t want to overwrite what is there in the environment variable already.
>> 
>> 
>> adding for example this in the Portfile:
>> 
>> configure.env-append "LDFLAGS=-Wl,-w”
>> 
>> 
>> adds my new LDFLAGS onto the existing LDFLAGS in the environment, as far as I can tell.
>> 
>> without:
>> LDFLAGS='-L/opt/universalnew/lib -Wl,-headerpad_max_install_names -Wl,-syslibroot,/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.13.sdk -arch x86_64 -arch i386'
>> 
>> with:
>> LDFLAGS='-Wl,-w -L/opt/universalnew/lib -Wl,-headerpad_max_install_names -Wl,-syslibroot,/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.13.sdk -arch x86_64 -arch i386'
>> 
>> 
>> So that works (better than I initially thought, actually).
>> 
>> 
>> However, as we previously noted in another ticket exploring this:
>> 
>> ${configure.ldflags}
>> 
>> does not pick up any of the modifications that are done to LDFLAGS in portconfigure.tcl or in Portfile, and so is, practically, seriously flawed:
>> 
>> pre-build {
>>   puts ${configure.ldflags}
>> }
>> 
>> -L/opt/universalnew/lib -Wl,-headerpad_max_install_names
>> 
>> 
>> Have we discovered a way in the Portfile to force ${configure.ldflags} to be updated to be the same as the fully processed LDFLAGS in configure.env?
> 
> No... it's the other way around...
> 
> If you want to modify LDFLAGS, do so by modifying configure.ldflags. MacPorts will set the LDFLAGS environment variable to the value of  configure.ldflags before running the configure phase.
> 
> This is the reason why we have all these configure.* variables: to make it easy/possible to set/append/prepend/replace values in commonly-used environment variables.
> 
> Of course this only works for environment variables for which we've had the foresight to provide a configure.* variable. If the variable you want to do this for doesn't currently have one, and if it's of general enough interest, a variable could be added to base for that.
> 
> For commonly-used environment variables for which we have configure.* variables, like configure.ldflags, don't attempt to manually set/append/whatever LDFLAGS in configure.env. Instead, use the variable MacPorts has provided.

Maybe the MacPorts could raise an error if one attempts to set a variable like LDFLAGS outside of configure.* ?

Blair