[MacPorts] #41124: graphviz uses a fuzzy check whether alloca(3) uses malloc(3), which fails in some cases

[MacPorts]

#41124: graphviz uses a fuzzy check whether alloca(3) uses malloc(3), which fails
in some cases
--------------------+--------------------------
 Reporter:  cal@…   |      Owner:  ryandesign@…
     Type:  defect  |     Status:  new
 Priority:  Normal  |  Milestone:
Component:  ports   |    Version:  2.2.1
 Keywords:          |       Port:  graphviz
--------------------+--------------------------
 Graphviz uses a check in `lib/vmalloc/features/vmalloc` that is supposed
 to find out whether `alloca(3)` is internally using `malloc(3)`. To do
 this, this check provides a custom implementation of `malloc(3)` and
 assumes that if this implementation is going to be called it was called by
 `alloca(3)`.

 However, this assumption doesn't hold in all cases, e.g. it breaks when
 having `DYLD_INSERT_LIBRARIES` is set, as is the case for trace mode,
 because the Mac OS loader `dyld` internally calls `malloc(3)`, causing the
 check to fail.

 The check should instead use a global volatile variable to check whether
 the current call to `malloc(3)` happened while trying to use `alloca(3)`.
 The overriden `malloc(3)` should behave like the standard one in all other
 cases.

 The attached patch fixes this. Additional checks for `dlsym(3)` and
 `dlfcn.h` might be required. Can you take this upstream? I assume the same
 applies to `graphviz-devel`, too.

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Ticket URL: <https://trac.macports.org/ticket/41124>
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