Re: Bug in make-3.81: variable_buffer moves out from under buffer

[David Wuertele]

Martin Dorey <mdorey <at> bluearc.com> writes:

> And it looks like there are several other instances of it too.

That's what I was afraid of.  I looked at the other places where xrealloc
could get called, but I couldn't find any that referenced the original buffer
address after the xrealloc.  I suspected that I might have missed some ---
xrealloc is used really heavily.

> >> What I am looking for is some help writing a makefile that
> >> is simple enough to post in a bug report.
> 
> I had a few goes but it looks like the variable_buffer is always already
> big enough by the time it gets here.  Can you tell us what rule it falls
> over on for you or what trickery might be associated with that rule?  Is
> there, for example, re-reading of makefiles going on, or $(eval) magic?

It is a static pattern rule, during the following function:

main() -> snap_deps() -> expand_deps() 

This function calls patsubst_expand() on the rule target, and when
patsubst_expand returns, the original buffer contents have moved.

I tried reducing my makefile to just the two rules that trigger the bug (one
that sets variable_buffer to the default size of 200, and one that busts beyond
it), but somehow I can't get the variable_buffer to stay at 200 before it gets
to the static pattern rule.  Here's what I expected the reduced makefile to
look like:

a1: a%: b%; @echo trash

a2222222222222222222222222222222222222222222222222222222222222222222222222222\
2222222222222222222222:
a22222222222222222222222222222222222222222%:
c%22222222222222222222222222222222222222222222; @echo trash

But somehow the variable_buffer is already big enough when it gets to the
long rule.

Dave