On 2013-11-17 5:39 PM, Mike Hommey wrote:
On Sat, Nov 16, 2013 at 10:34:38AM +0100, Ms2ger wrote:
On 11/14/2013 11:49 PM, Ehsan Akhgari wrote:
I've started to work on a project in my spare time to switch us to use
unified builds for C/C++ compilation. The way that unified builds work is
by using the UNIFIED_SOURCES instead of the SOURCES variable in moz.build
files. With that, the build system creates files such as:
// Unified_cpp_path_0.cpp
#include "Source1.cpp"
#include "Source2.cpp"
// ...
And compiles them instead of the individual source files.
One issue I only thought of today: this means that Source2.cpp can
use all headers included into Source1.cpp–until enough files are
added between Source1 and Source2 that Source2 ends up in the next
unified file. This hasn't been much of an issue for autogenerated
C++, but it seems like it could be harder to get right with
hand-written C++.
One way around it would be not to unify sources in automation. On
one hand, this could cause more bustage when changes that built
locally turn out not to have enough includes; on the other, it might
be better than having to fix up a dozen unrelated files whenever you
add a new one.
Another related problem is that of conflicting function or variable
names, macros, etc. We're obviously fixing those when they need to be
when unifying files in a given directory, but there is a chance a
conflict is introduced by a file moving from Unified1 to Unified2.
Yes, although I'm trying to be a bit smart here and look around for that
kind of problem when it's obvious in the patches that I write for this.
Cheers,
Ehsan
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