[MacPorts] UniversalDevelopment modified

[MacPorts]

Page "UniversalDevelopment" was changed by egall at gwmail.gwu.edu
Diff URL: <https://trac.macports.org/wiki/UniversalDevelopment?action=diff&version=6>
Revision 6
Comment: Give more examples and descriptions of how and when to use these different universal building methods
Changes:
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Index: UniversalDevelopment
=========================================================================
--- UniversalDevelopment (version: 5)
+++ UniversalDevelopment (version: 6)
@@ -1,11 +1,46 @@
 Port(1) supports for universal builds is not good enough to handle non-trivial cases. We currently try to develop mechanisms to overcome this, so we can make more ports build universal more easily.
 
 === Approaches ===
- * Adding the universal build flags (''-arch ppc -arch ppc64 ..'') to the compiler flags: Suited for straight compilation of executables
- * Adding universal build flags to the CFLAGS etc.: Suited for certain autotool driven builds
+ * Adding the universal build flags ("-arch i386 -arch x86_64 ...") to the compiler flags (i.e. the "CC" environment variable itself): Suited for straight compilation of executables. This is usually done for hand-written Makefiles and often has to be done manually from the Portfile. For example, if the `build.cmd` is `make`, the code in the Portfile would look something like this:
+{{{
+build.args-append CC="${configure.cc} [get_canonical_archflags cc]"
+}}}
+ You could also try setting it in `build.env`, but sometimes `make` does not respect environment variables if that variable is not also used as a Makefile variable, so it is safer just to force it in `build.args`.
+ * Adding universal build flags to the CFLAGS etc.: Suited for certain autotools-driven builds. This is done by default. The default values for these universal flags vary by platform. On Tiger on PowerPC, they are:
+{{{
+configure.universal_cflags -isysroot ${developer_dir}/SDKs/MacOSX10.4u.sdk -arch i386 -arch ppc
+configure.universal_cppflags -isysroot ${developer_dir}/SDKs/MacOSX10.4u.sdk
+configure.universal_cxxflags -isysroot ${developer_dir}/SDKs/MacOSX10.4u.sdk -arch i386 -arch ppc
+configure.universal_ldflags -Wl,-syslibroot,${developer_dir}/SDKs/MacOSX10.4u.sdk -arch i386 -arch ppc
+}}}
+ On Tiger on Intel and on Leopard, they are:
+{{{
+configure.universal_cflags -arch i386 -arch ppc
+configure.universal_cxxflags -arch i386 -arch ppc
+configure.universal_ldflags -arch i386 -arch ppc
+}}}
+ On Snow Leopard and later, they are:
+{{{
+configure.universal_cflags -arch x86_64 -arch i386
+configure.universal_cxxflags -arch x86_64 -arch i386
+configure.universal_ldflags -arch x86_64 -arch i386
+}}}
+ The exception is `configure.universal_args`, which has the same default across platforms:
+{{{
+configure.universal_args --disable-dependency-tracking
+}}}
  * Adding universal build flags to the libtool command e.g. `reinplace "s|CC -dynamiclib|CC -dynamiclib ${configure.universal_ldflags}|g" ${worksrcpath}/libtool`
- * Separating builds for different architectures, merging the different (single-arch) destroots: See the muniversal portgroup (emulation or multiple build machines differing in arch may be necessary for some ports)
-
+ * Separating builds for different architectures, merging the different (single-arch) destroots: See the [browser:trunk/dports/_resources/port1.0/group/muniversal-1.0.tcl muniversal PortGroup] (emulation or multiple build machines differing in arch may be necessary for some ports). This is useful in various different situations:
+  - When the port tries to use the `--enable-dependency-tracking` configure flag anyways, which makes building normally result in an error like this:
+{{{
+gcc-4.2: -E, -S, -save-temps and -M options are not allowed with multiple -arch flags
+}}}
+  - When the build system tries to put a fat archive inside another archive, resulting in an error like this:
+{{{
+/opt/local/bin/ranlib: archive member: libtcs.a(libtddl.a) fat file for cputype (16777223) cpusubtype (3) is not an object file (bad magic number)
+}}}
+  (this works when the archive is '''not''' fat)
+  - When the build system has architecture-specific assembly, or otherwise builds files differently based on architecture.
 
 === Developers ===
 [wiki:mww mww (Markus W. Weissmann)]
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