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libcutils: vendor_available

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By setting vendor_available, the following may become true:

* a prebuilt library from this release may be used at runtime by
  in a later releasse (by vendor code compiled against this release).
  so this library shouldn't depend on runtime state that may change
  in the future.
* this library may be loaded twice into a single process (potentially
  an old version and a newer version). The symbols will be isolated
  using linker namespaces, but this may break assumptions about 1
  library in 1 process (your singletons will run twice).

Background:

This means that these modules may be built and installed twice --
once for the system partition and once for the vendor partition. The
system version will build just like today, and will be used by the
framework components on /system. The vendor version will build
against a reduced set of exports and libraries -- similar to, but
separate from, the NDK. This means that all your dependencies must
also mark vendor_available.

At runtime, /system binaries will load libraries from /system/lib*,
while /vendor binaries will load libraries from /vendor/lib*. There
are some exceptions in both directions -- bionic(libc,etc) and liblog
are always loaded from /system. And SP-HALs (OpenGL, etc) may load
/vendor code into /system processes, but the dependencies of those
libraries will load from /vendor until it reaches a library that's
always on /system. In the SP-HAL case, if both framework and vendor
libraries depend on a library of the same name, both versions will be
loaded, but they will be isolated from each other.

It's possible to compile differently -- reducing your source files,
exporting different include directories, etc. For details see:

https://android-review.googlesource.com/368372

None of this is enabled unless the device opts into the system/vendor
split with BOARD_VNDK_VERSION := current.

Bug: 36426473
Bug: 36079834
Test: m -j libcutils
Test: attempt to compile with BOARD_VNDK_VERSION := current
Test: (sanity) boot internal marlin
Change-Id: I76f9b28ef08a26d84d1365881e00696cc1dcfe5d
This commit is contained in:
Steven Moreland 2017-04-13 14:29:58 -07:00
parent 421067e040
commit 9610c548a8
1 changed files with 5 additions and 6 deletions
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11
libcutils/Android.bp
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@ -30,17 +30,15 @@ libcutils_nonwindows_sources = [
"str_parms.c",
]
cc_library_headers {
name: "libcutils_vndk_headers",
host_supported: true,
export_include_dirs: ["include_vndk"],
}
cc_library_headers {
name: "libcutils_headers",
vendor_available: true,
host_supported: true,
export_include_dirs: ["include"],
target: {
vendor: {
export_include_dirs: ["include_vndk"],
},
linux_bionic: {
enabled: true,
},
@ -52,6 +50,7 @@ cc_library_headers {
cc_library {
name: "libcutils",
vendor_available: true,
host_supported: true,
srcs: [
"config_utils.c",