Handle shift by 32 explicitly.

Looks like it worked before due to undefined behavior always returning 0. But not anymore. Test: 836-32768classes Bug: 220821265 Change-Id: Iaaefc0d3237cf3b6bf50798097b98a8004089d7c
AOSPA · Feb 23, 2022 · b875631 · b875631
1 parent 36de6a2
commit b875631
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Showing 6 changed files with 5 additions and 2 deletions.
diff --git a/libdexfile/dex/type_lookup_table.cc b/libdexfile/dex/type_lookup_table.cc
@@ -107,7 +107,7 @@ uint32_t TypeLookupTable::Lookup(const char* str, uint32_t hash) const {
     return dex::kDexNoIndex;
   }
   // Look for the partial hash match first, even if traversing the wrong bucket's chain.
-  uint32_t compared_hash_bits = (hash << mask_bits_) >> (2 * mask_bits_);
+  uint32_t compared_hash_bits = static_cast<uint64_t>(hash << mask_bits_) >> (2 * mask_bits_);
   while (compared_hash_bits != entry->GetHashBits(mask_bits_)) {
     if (entry->IsLast(mask_bits_)) {
       return dex::kDexNoIndex;

diff --git a/libdexfile/dex/type_lookup_table.h b/libdexfile/dex/type_lookup_table.h
@@ -147,7 +147,7 @@ class TypeLookupTable {
 
     uint32_t GetHashBits(uint32_t mask_bits) const {
       DCHECK_LE(mask_bits, 16u);
-      return data_ >> (2u * mask_bits);
+      return static_cast<uint64_t>(data_) >> (2u * mask_bits);
     }
 
     static uint32_t GetMask(uint32_t mask_bits) {

diff --git a/test/836-32768classes/classes.dex b/test/836-32768classes/classes.dex
diff --git a/test/836-32768classes/expected-stderr.txt b/test/836-32768classes/expected-stderr.txt
diff --git a/test/836-32768classes/expected-stdout.txt b/test/836-32768classes/expected-stdout.txt
@@ -0,0 +1 @@
+Hello World!
diff --git a/test/836-32768classes/info.txt b/test/836-32768classes/info.txt
@@ -0,0 +1,2 @@
+Regression test for a dex file with 32768 classes. We used to rely on undefined
+shift behavior in the type lookup table code.
Original file line number	Diff line number	Diff line change
		@@ -0,0 +1,2 @@
		Regression test for a dex file with 32768 classes. We used to rely on undefined
		shift behavior in the type lookup table code.