Issue ID: 19159
           Summary: `alloca` does not work in -betterC
           Product: D
           Version: D2
          Hardware: All
                OS: All
            Status: NEW
          Severity: normal
          Priority: P1
         Component: dmd

extern(C) void main()
    import core.stdc.stdlib : alloca;

    enum length = 20;
    auto msg = (cast(char*)alloca(length))[0 .. length];

$ dmd -betterC main.d
error: undefined reference to '__alloca'
collect2: error: ld returned 1 exit status
Error: linker exited with status 1

Works fine with LDC, however:

Also, `alloca` should not be in `core.stdc.stdlib`; it's not a standard C

It may also be better to allocate static arrays on the stack when their length
is supplied at runtime.  See 
That would make `alloca` and `__alloca` just an implementation detail that
users wouldn't even need to use directly.


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