Revert "[scudo] Fix MallocIterateBoundary on 32 bit."

[cferris]

Summary

This reverts commit 5e691a1c9b0ad22689d4a434ddf4fed940e58dec.

[cferris]

This breaks the test when running on x86_64. I suspect the test is depending on the size classes in some way.

[Chia-hungDuan]

In D152779#4416433, @cferris wrote:

This breaks the test when running on x86_64. I suspect the test is depending on the size classes in some way.

qq, is this the same failure that we see on Android? Can't find the block aligned at page boundary?

[cferris]

It appears to be the same one, but on x86. As I mentioned, my guess is this depends on the sizeclasses.

One idea I had was to try the 8 size, then the 16 size. But I want to understand this in more detail so that it still tests what it was meant to test.

compiler-rt/lib/scudo/standalone/tests/wrappers_c_test.cpp

 }
 
 // Verify that a block located on an iteration boundary is not mis-accounted.
 // To achieve this, we allocate a chunk for which the backing block will be
 // aligned on a page, then run the malloc_iterate on both the pages that the
 // block is a boundary for. It must only be seen once by the callback function.
 TEST(ScudoWrappersCTest, MallocIterateBoundary) {
   const size_t PageSize = sysconf(_SC_PAGESIZE);
-  const size_t BlockDelta = 16U;
+  const size_t BlockDelta = FIRST_32_SECOND_64(8U, 16U);
   const size_t SpecialSize = PageSize - BlockDelta;
 
   // We aren't guaranteed that any size class is exactly a page wide. So we need
   // to keep making allocations until we succeed.
   //
   // With a 16-byte block alignment and 4096-byte page size, each allocation has
   // a probability of (1 - (16/4096)) of failing to meet the alignment
   // requirements, and the probability of failing 65536 times is