Hi Mark,
Thanks for the detailed explanation! I just landed a fix based on your
suggestions. It built okay with both the wx and Apple ports, but if it
causes anyone trouble, please let me know!
Thanks,
Kevin
On Mar 14, 2009, at 7:31 PM, Mark Rowe wrote:
On 2009-03-14, at 10:49, Kevin Ollivier wrote:
Hi all,
I'm seeing some strangeness with the OS X availability macros.
First, it looks like BUILDING_ON_TIGER and BUILDING_ON_LEOPARD are
defined in JavaScriptCorePrefix.h, which AFAICT is only used by the
Apple XCode projects, yet the use of these macros are often inside
PLATFORM(DARWIN) rather than PLATFORM(MAC) checks, meaning other
ports building on Mac will need them too. Second, even after I
tried moving them to Platform.h, the MAX_ALLOWED <=
MAC_OS_X_VERSION_10_5 check doesn't work for me, because apparently
MAX_ALLOWED is defined to the actual latest release on my machine
(1056) rather than (1050), and so the check doesn't pass and so it
sets things up as if I'm running something post-Leopard, which I
only wish I were doing... ;-) Checking MAX_ALLOWED <= 1056 does get
things going right again.
The use of the BUILDING_ON macros inside PLATFORM(DARWIN) blocks may
all be recent additions. I introduced one such use earlier this
week, and I believe Darin may have done so as well. I'm not sure
whether there were any instances of this prior to those two
changes. Moving the macro definitions in to wtf/Platform.h so that
they can be used by other ports building on Mac OS X seems
reasonable to me, but we may need to tweak them slightly to work
with ports that aren't aware of the SDK and deployment target
mechanisms that Mac OS X's compiler toolchain provides.
For some background: the way these macros are intended to function
is that MAC_OS_X_VERSION_MIN_REQUIRED indicates the minimum version
of the operating system that the binary will run on, while
MAC_OS_X_VERSION_MAX_ALLOWED indicates the maximum version of the
operating system that you intend to take advantage of. Symbols
introduced in OS versions between MAC_OS_X_VERSION_MIN_REQUIRED and
MAC_OS_X_VERSION_MAX_ALLOWED will be weak-linked, and symbols
introduced after MAC_OS_X_VERSION_MAX_ALLOWED will be unavailable
for use.
When building via Xcode these values are typically derived from two
configuration settings: the SDK that your project is targeting
(corresponding to GCCs -isysroot argument), and the deployment
target (-mmacosx-version-min). If you build against the MacOSX10.5
SDK with a deployment target of 10.4 you will see that
MAC_OS_X_VERSION_MIN_REQUIRED is set to 1040 and
MAC_OS_X_VERSION_MAX_ALLOWED is set to 1050.
If you don't build against an SDK or specify a deployment target
then both MAC_OS_X_VERSION_MIN_REQUIRED and
MAC_OS_X_VERSION_MAX_ALLOWED will default to your current Mac OS X
version (eg, 1056), and the compiler happily let you use
functionality that would prevent your application from running on
previous versions of Mac OS X.
The Mac build of WebKit explicitly sets a deployment target equal to
the major version of the Mac OS X version that you are on. This
results in both MAC_OS_X_VERSION_MIN_REQUIRED and
MAC_OS_X_VERSION_MAX_ALLOWED being set to the major component of the
Mac OS X version (eg, 1050).
Since the wxWidgets build of WebKit doesn't build against an SDK or
explicitly set a deployment target, it is seeing
MAC_OS_X_VERSION_MAX_ALLOWED set to 1056 where the Mac build sees
1050. This is why the checks that set BUILDING_ON_LEOPARD aren't
working for you.
I think we could rephrase the checks to accommodate building without
an SDK and deployment target. Something like the following should
do the trick:
#if !defined(MAC_OS_X_VERSION_10_5) || MAC_OS_X_VERSION_MAX_ALLOWED
< MAC_OS_X_VERSION_10_5
#define BUILDING_ON_TIGER 1
#if !defined(MAC_OS_X_VERSION_10_6) || MAC_OS_X_VERSION_MAX_ALLOWED
< MAC_OS_X_VERSION_10_6
#define BUILDING_ON_LEOPARD 1
#endif
I hope this clears things up. Let me know if you have any questions!
- Mark
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