[LLVMbugs] [Bug 7490] New: Incomplete default initialization of arrays

[bugzilla-daemon at llvm.org]

http://llvm.org/bugs/show_bug.cgi?id=7490

           Summary: Incomplete default initialization of arrays
           Product: clang
           Version: trunk
          Platform: PC
        OS/Version: Linux
            Status: NEW
          Severity: normal
          Priority: P
         Component: C++
        AssignedTo: unassignedclangbugs at nondot.org
        ReportedBy: collinwinter at google.com
                CC: chandlerc at gmail.com, llvmbugs at cs.uiuc.edu,
                    dgregor at apple.com, jyasskin at google.com


Created an attachment (id=5108)
 --> (http://llvm.org/bugs/attachment.cgi?id=5108)
Reduced test case

It appears Clang does not default-initialize all elements of an array. The
attached program passes with gcc but fails with Clang built from r106806
(x86-64 Linux).

If I install a malloc() that poisons memory, something like "new int[2]()"
should zero out both bytes. Clang currently only zeros the first element.

The problem reproduces easily when linking against tcmalloc's debug allocator:

0) Install tcmalloc from
http://google-perftools.googlecode.com/files/google-perftools-1.5.tar.gz to
/tmp/tcmalloc
1) clang -lstdc++ -L/tmp/tcmalloc/lib -Wl,--rpath=/tmp/tcmalloc/lib
-ltcmalloc_debug intrusive_hash_map_test.cc -o intrusive_hash_map_test &&
./intrusive_hash_map_test && echo "Test passed"

The program fails with an assertion error when compiled with Clang.

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