[Issue 19290] New: immutable associative array corruption with -m64 and MinGW

[d-bugmail at puremagic.com]

https://issues.dlang.org/show_bug.cgi?id=19290

          Issue ID: 19290
           Summary: immutable associative array corruption with -m64 and
                    MinGW
           Product: D
           Version: D2
          Hardware: x86_64
                OS: Windows
            Status: NEW
          Severity: critical
          Priority: P1
         Component: dmd
          Assignee: nobody at puremagic.com
          Reporter: b2.temp at gmx.com

It seems that a kind of corruption happens in dparse when it's compiled with
-m64, lld linker and MinGW.

To reproduce save this code in a bat and run it from a console:

```
git clone https://github.com/dlang-community/libdparse.git
git clone https://github.com/dlang-community/stdx-allocator.git

cd libdparse
git checkout v0.9.9
cd ..

dmd main.d ^
libdparse\src\std\experimental\lexer.d ^
libdparse\src\dparse\ast.d ^
libdparse\src\dparse\lexer.d ^
libdparse\src\dparse\parser.d ^
libdparse\src\dparse\rollback_allocator.d ^
libdparse\src\dparse\stack_buffer.d ^
stdx-allocator\source\stdx\allocator\package.d ^
stdx-allocator\source\stdx\allocator\mallocator.d ^
stdx-allocator\source\stdx\allocator\gc_allocator.d ^
-Ilibdparse\src -Istdx-allocator\source -m64 -debug

main.exe
```

Which gives a range error that didn't happen when using -m32, here :

https://github.com/dlang-community/libdparse/blob/95444a966923a24098c31464e09a7096208da155/src/dparse/ast.d#L88

This really shouldn't happen since each possible entry is setup in a static
module constructor just above.
The problem doesn't happen if the involved assoc array is not immutable, which
will be used as workaround for now. (test case wont be affected)

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