4 ms·

> What exactly are all of you people doing with your laptops? C/C++ project builds. Losing two cores just about doubles build times, and template-heavy C++ co

> What exactly are all of you people doing with your laptops? C/C++ project builds. Losing two cores just about doubles build times, and template-heavy C++ code makes the compiler want gigs of RAM all to itself. In principle I should do this on a desktop or server, but IT isn't on board with that.

gkya 9y ago
Do you do full recompilations all the time? Don't you use incremental builds? If yes, the compilation time should only rarely be a problem. But reading people's comments I feel like there are many projects out there using a shell script like "gcc -c a.cpp; gcc -c b.cpp; ...; gcc -o prog *.o" out there.
- nine_k 9y ago
  Changing something closer to the root of a large dependency tree triggers a lot of recompilation. The lack of real modules and reliance of `#include` in C++ makes dependency graphs larger than they could be.
  - gkya 9y ago
    Not necessarily. Say I'm editing "bob.cc", and in the mean time edited "common.h" #included by many many files. While I'm editing "bob.cc", there is no need for me to rebuild the entire project until I want to see how it links to everything else (which can be postponed quite a bit if you have some tests); so I either run "make bob.cc" or "make test_bob.cc && ./test_bob". I don't know much C++ and all this is theoretical, but I think this is the ideal workflow with C/C++ development, and this is why incremental builds are useful, especially if the code is nicely separated into testable units.
- 0xcde4c3db 9y ago
  Not full recompilations, but when we're working on a feature release, switching git branches routinely requires a lot of files to be rebuilt due to header changes.
  - craftyguy 9y ago
    ccache is your friend.
- munin 9y ago
  When you use templates, recompiling a single file can take ten minutes.
  - gkya 9y ago
    Is there an open source project where I can test this? I don't know much about C++ (I know some C), and would like to see this for myself.
nookoking 9y ago
I have to agree with the other poster on this. I only full compile once in the beginning and once at the end. Every other time, I just recompile the changed part and rebuild it with the unchanged object files. But if you're talking about packages from source, then I agree. It's the one thing that sometimes makes me question whether or not I should upgrade. But, after a full night of compiling Qt5 from source, that lingering doubt usually vanishes.

gkya 9y ago

Do you do full recompilations all the time? Don't you use incremental builds? If yes, the compilation time should only rarely be a problem. But reading people's comments I feel like there are many projects out there using a shell script like "gcc -c a.cpp; gcc -c b.cpp; ...; gcc -o prog *.o" out there.

nine_k 9y ago
Changing something closer to the root of a large dependency tree triggers a lot of recompilation. The lack of real modules and reliance of `#include` in C++ makes dependency graphs larger than they could be.
- gkya 9y ago
  Not necessarily. Say I'm editing "bob.cc", and in the mean time edited "common.h" #included by many many files. While I'm editing "bob.cc", there is no need for me to rebuild the entire project until I want to see how it links to everything else (which can be postponed quite a bit if you have some tests); so I either run "make bob.cc" or "make test_bob.cc && ./test_bob". I don't know much C++ and all this is theoretical, but I think this is the ideal workflow with C/C++ development, and this is why incremental builds are useful, especially if the code is nicely separated into testable units.
0xcde4c3db 9y ago
Not full recompilations, but when we're working on a feature release, switching git branches routinely requires a lot of files to be rebuilt due to header changes.
- craftyguy 9y ago
  ccache is your friend.
munin 9y ago
When you use templates, recompiling a single file can take ten minutes.
- gkya 9y ago
  Is there an open source project where I can test this? I don't know much about C++ (I know some C), and would like to see this for myself.

nookoking 9y ago

I have to agree with the other poster on this. I only full compile once in the beginning and once at the end. Every other time, I just recompile the changed part and rebuild it with the unchanged object files. But if you're talking about packages from source, then I agree. It's the one thing that sometimes makes me question whether or not I should upgrade. But, after a full night of compiling Qt5 from source, that lingering doubt usually vanishes.