Scons Explicit Dependency -

i have simple .cpp file depends on jsoncpp. part of build process want scons untar jsoncpp (if isn't already) , build (if isn't already) before attempting compile app.cpp since app.cpp depends on .h files zipped inside of jsoncpp.tar.gz.

this i've tried far:

env = environment() env.program('app', 'app.cpp') env.depends('app.cpp', 'jsoncpp')  def build_jsoncpp(target, source, env):     shutil.rmtree("jsoncpp", ignore_errors=true)     mytar = tarfile.open(str(source[0]))     mytar.extractall()     print("extracted jsoncpp")  env.command("jsoncpp", ['jsoncpp.tar.gz'], build_jsoncpp) 

however, scons never prints "extracted jsoncpp"... attempts compile app.cpp , promptly fails.

if using make, like:

app: jsoncpp.tar.gz     # build app  jsoncpp.tar.gz:     # extract , build here 

and order guaranteed.

you should take @ untarbuilder, means extract tarfile , have of extracted files inserted dependency tree. following have working.

you want avoid explicit dependencies, if possible. 1 of many joys of scons letting take care of dependencies you. list source file depending on 1 of targets of untar command builder.

to test created tar file called jsoncpp.tar.gz containing 1 file, app.cpp, following contents.

#include <iostream> int main() {     std::cout << "hello world" << std::endl;     return 0; } 

and updated sconstruct following.

import shutil import tarfile  env = environment() env.program('app', 'app.cpp')  def build_jsoncpp(target, source, env):     shutil.rmtree("jsoncpp", ignore_errors=true)     mytar = tarfile.open(str(source[0]))     mytar.extractall()     print("extracted jsoncpp")  env.command(["app.cpp"], ['jsoncpp.tar.gz'], build_jsoncpp) 

because list required source file depend on target of command builder, handle dependencies you.

and when run, see following.

>> scons --version scons steven knight et al.:     script: v2.3.4, 2014/09/27 12:51:43, garyo on lubuntu     engine: v2.3.4, 2014/09/27 12:51:43, garyo on lubuntu     engine path: ['/usr/lib/scons/scons'] copyright (c) 2001 - 2014 scons foundation  >> tree . ├── jsoncpp.tar.gz └── sconstruct  0 directories, 2 files  >> scons scons: reading sconscript files ... scons: done reading sconscript files. scons: building targets ... build_jsoncpp(["app.cpp"], ["jsoncpp.tar.gz"]) extracted jsoncpp g++ -o app.o -c app.cpp g++ -o app app.o scons: done building targets.  >> tree . ├── app ├── app.cpp ├── app.o ├── jsoncpp.tar.gz └── sconstruct  0 directories, 5 files  >> ./app hello world 

the reason why code not work because listing jsoncpp target of untar command builder. not file compiling app.cpp depend on, if list action explicit dependency.

while doesn't answer question, hope provides solution trying accomplish.