Fix backwards compat problem with AAPT public attrs

AAPT has traditionally assigned resource IDs to public attributes,
and then followed those public definitions with private attributes.

--- PUBLIC ---
| 0x01010234 | attr/color
| 0x01010235 | attr/background

--- PRIVATE ---
| 0x01010236 | attr/secret
| 0x01010237 | attr/shhh

Each release, when attributes are added, they take the place of the private
attributes and the private attributes are shifted down again.

--- PUBLIC ---
| 0x01010234 | attr/color
| 0x01010235 | attr/background
| 0x01010236 | attr/shinyNewAttr
| 0x01010237 | attr/highlyValuedFeature

--- PRIVATE ---
| 0x01010238 | attr/secret
| 0x01010239 | attr/shhh

Platform code may look for private attributes set in a theme. If an app
compiled against a newer version of the platform uses a new public
attribute that happens to have the same ID as the private attribute
the older platform is expecting, then the behavior is undefined.

We get around this by detecting any newly defined attributes (in L),
copy the resource into a -v21 qualified resource, and delete the
attribute from the original resource. This ensures that older platforms
don't see the new attribute, but when running on L+ platforms, the
attribute will be respected.

We still need to address this problem in the platform moving forward,
as this will only help us in the transition from pre L to L.

Bug:17520380
Change-Id: Ia2a985798b50006c21c7c3431d30d9598f27cd91

2 files changed, 41 insertions, 1 deletions

diff --git a/libs/androidfw/ResourceTypes.cpp b/libs/androidfw/ResourceTypes.cpp
index 690b1d6..8cef137 100644
--- a/libs/androidfw/ResourceTypes.cpp
+++ b/libs/androidfw/ResourceTypes.cpp
@@ -5393,6 +5393,44 @@ const char16_t* StringPoolRef::string16(size_t* outLen) const {
     return NULL;
 }
 
+bool ResTable::getResourceFlags(uint32_t resID, uint32_t* outFlags) const {
+    if (mError != NO_ERROR) {
+        return false;
+    }
+
+    const ssize_t p = getResourcePackageIndex(resID);
+    const int t = Res_GETTYPE(resID);
+    const int e = Res_GETENTRY(resID);
+
+    if (p < 0) {
+        if (Res_GETPACKAGE(resID)+1 == 0) {
+            ALOGW("No package identifier when getting flags for resource number 0x%08x", resID);
+        } else {
+            ALOGW("No known package when getting flags for resource number 0x%08x", resID);
+        }
+        return false;
+    }
+    if (t < 0) {
+        ALOGW("No type identifier when getting flags for resource number 0x%08x", resID);
+        return false;
+    }
+
+    const PackageGroup* const grp = mPackageGroups[p];
+    if (grp == NULL) {
+        ALOGW("Bad identifier when getting flags for resource number 0x%08x", resID);
+        return false;
+    }
+
+    Entry entry;
+    status_t err = getEntry(grp, t, e, NULL, &entry);
+    if (err != NO_ERROR) {
+        return false;
+    }
+
+    *outFlags = entry.specFlags;
+    return true;
+}
+
 status_t ResTable::getEntry(
         const PackageGroup* packageGroup, int typeIndex, int entryIndex,
         const ResTable_config* config,
diff --git a/libs/androidfw/tests/data/basic/build b/libs/androidfw/tests/data/basic/build
index fa4a9fe..036e468 100755
--- a/libs/androidfw/tests/data/basic/build
+++ b/libs/androidfw/tests/data/basic/build
@@ -1,6 +1,8 @@
 #!/bin/bash
 
-aapt package -M AndroidManifest.xml -S res --split fr,de -F bundle.apk -f && \
+PATH_TO_FRAMEWORK_RES=$(gettop)/prebuilts/sdk/current/android.jar
+
+aapt package -M AndroidManifest.xml -S res -I $PATH_TO_FRAMEWORK_RES --split fr,de -F bundle.apk -f && \
 unzip bundle.apk resources.arsc && \
 mv resources.arsc basic.arsc && \
 xxd -i basic.arsc > basic_arsc.h && \