[Chicken-hackers] [PATCH] Fix seemingly random crashes in foreign callbacks (#1337)

[Peter Bex]

Hi all,

The attached patch fixes #1337, which has exactly the same root cause as
the "Salmonella crashes a lot" issue we struggled with back in 2015:
http://lists.gnu.org/archive/html/chicken-hackers/2015-10/msg00001.html

I guess we never noticed this because the circumstances are relatively
rare:  You have to use a foreign callback which calls code that triggers
a GC, and this GC needs to happen before the argvector is copied onto
the stack by an intermediate function that happens to call another
function with a larger number of arguments.

I don't know how to make a test case for this that reliably triggers the
error.  The test case from the ticket happens to trigger it now, but it
might not in the future.

I also noticed that when the stack is full in C_allocate_vector, we call
C_reclaim(allocate_vector_2, c), but we save one more thing than the
number of arguments allocate_vector takes.

Cheers,
Peter

0001-Fix-crashes-in-callbacks-after-GC-1337.chicken-5.patch
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0001-Fix-crashes-in-callbacks-after-GC-1337.master.patch
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