[Issue 21393] New: core.thread.fiber: ignores RAM allocation if mmap/valloc/malloc not found

[d-bugmail at puremagic.com]

https://issues.dlang.org/show_bug.cgi?id=21393

          Issue ID: 21393
           Summary: core.thread.fiber: ignores RAM allocation if
                    mmap/valloc/malloc not found
           Product: D
           Version: D2
          Hardware: All
                OS: Other
            Status: NEW
          Severity: normal
          Priority: P1
         Component: druntime
          Assignee: nobody at puremagic.com
          Reporter: feklushkin.denis at gmail.com

Code inside of fiber.d silently ignores RAM allocation if all of
mmap/valloc/malloc calls is not detected by __traits( compiles, xxx ).

Expected behavior: compilation error.

Related unsucessful PR: https://github.com/dlang/druntime/pull/3241

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