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authorNat Goodspeed <nat@lindenlab.com>2019-06-27 10:57:34 -0400
committerNat Goodspeed <nat@lindenlab.com>2020-03-25 18:44:04 -0400
commit2902f23a4193d93c2e96daa45587a8c597c0a831 (patch)
tree96655824fd61c58335a388418b3a9147a1ce80fc /.hgtags
parent3a7d40136415fbf1897d5240ef4e4d48f79c8a26 (diff)
DRTVWR-476: Remove special llcorehttp test memory manager.
NickyD discovered that the substitute default allocator used for llcorehttp tests was returning badly-aligned storage, which caused access violations on alignment-sensitive data such as std::atomic. Thanks Nicky!! Moreover, the llcorehttp test assertions regarding memory usage, well- intentioned though they are, have been causing us trouble for years. Many have already been disabled. The problem is that use of test_allocator.h affected *everything* defined with that header file's declarations visible. That inevitably included specific functions in other subsystems. Those functions then (unintentionally) consumed the special allocator, throwing off the memory tracking and making certain memory-related assertions consistently fail. This is a particular, observable bad effect of One Definition Rule violations. Within a given program, C++ allows multiple definitions for the same entity, but requires that all such definitions be the same. Partial visibility of the global operator new() and operator delete() overrides meant that some definitions of certain entities used the default global allocator, some used llcorehttp's. There may have been other, more subtle bad effects of these ODR violations. If one wanted to reimplement verification of the memory consumption of llcorehttp classes: * Each llcorehttp class (for which memory tracking was desired) should declare class-specific operator new() and operator delete() methods. Naturally, these would all consume a central llcorehttp-specific allocator, but that allocator should *not* be named global operator new(). * Presumably that would require runtime indirection to allow using the default allocator in production while substituting the special allocator for tests. * Recording and verifying the memory consumption in each test should be performed in the test-object constructor and destructor, rather than being sprinkled throughout the test<n>() methods. * With that mechanism in place, the test object should provide methods to adjust (or entirely disable) memory verification for a particular test. * The test object should also provide a "yes, we're still consuming llcorehttp memory" method to be used for spot checks in the middle of tests -- instead of sprinkling in explicit comparisons as before. * In fact, the llcorehttp test object in each test_*.hpp file should be derived from a central llcorehttp test-object base class providing those methods.
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