[llvm-bugs] [Bug 45367] New: Aggregates containing elements with constexpr constructors are not statically initalized

[via llvm-bugs]

https://bugs.llvm.org/show_bug.cgi?id=45367

            Bug ID: 45367
           Summary: Aggregates containing elements with constexpr
                    constructors are not statically initalized
           Product: clang
           Version: 10.0
          Hardware: PC
                OS: Windows NT
            Status: NEW
          Severity: normal
          Priority: P
         Component: C++2a
          Assignee: unassignedclangbugs at nondot.org
          Reporter: billy.oneal at gmail.com
                CC: blitzrakete at gmail.com, erik.pilkington at gmail.com,
                    llvm-bugs at lists.llvm.org, richard-llvm at metafoo.co.uk

Created attachment 23295
  --> https://bugs.llvm.org/attachment.cgi?id=23295&action=edit
repro.cpp

Previously reported as https://github.com/microsoft/STL/issues/661

In the following example, should_be_statically_initalized should be eligible
for static initialization, then the dynamic initializer for foo that calls
bar() should run, resulting in the asserts in main(). However, clang only seems
to give these static initializers if the varaible is {}'d.

C:\Users\billy\Desktop>type repro.cpp
#include <assert.h>

struct FakeAtomic {
    int example;

    constexpr FakeAtomic() noexcept : example{} {}
    int operator++() { return ++example; }
    int operator++(int) { return example++; }
    int load() const { return example; }
};

struct Meow {
    FakeAtomic data[2];
    char padding[64];
};

int bar();

int foo = bar();
#ifdef WORKAROUND
Meow should_be_statically_initalized[256]{};
#else
Meow should_be_statically_initalized[256];
#endif

int bar() { return should_be_statically_initalized[0].data[0]++; }

int main() {
    assert(foo == 0);
    assert(should_be_statically_initalized[0].data[0].load() == 1);
}

C:\Users\billy\Desktop>clang-cl /EHsc /W4 /WX .\repro.cpp

C:\Users\billy\Desktop>.\repro.exe
Assertion failed: should_be_statically_initalized[0].data[0].load() == 1, file
.\repro.cpp, line 30

C:\Users\billy\Desktop>clang-cl /DWORKAROUND /EHsc /W4 /WX .\repro.cpp

C:\Users\billy\Desktop>.\repro.exe

C:\Users\billy\Desktop>

-- 
You are receiving this mail because:
You are on the CC list for the bug.
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.llvm.org/pipermail/llvm-bugs/attachments/20200331/34baff67/attachment-0001.html>