bug#53136: 28.0.90; segfault in lock_file

[Paul Eggert]

On 1/9/22 04:03, Eli Zaretskii wrote:

> Paul, could you please take a look?

The problem (as Po deduced) seems to be that Haiku errno values are 
negative by default.

However, I see some problems with the recently installed fix.

1. It uses BE_USE_POSITIVE_POSIX_ERRORS but Haiku spells it 
B_USE_POSITIVE_POSIX_ERRORS.

2. There's no need to replace "if (err < 0)" with "if (err == -1 || err 
== -2)", as this replacement is not needed given the "#if !defined HAIKU 
..." stuff.

3. More importantly, I'm sure there are other places where Emacs assumes 
that errno values are positive. I doubt whether it's reasonable to 
expect Emacs developers to remember and work around this Haiku 
incompatibility, every time they call a function that sets errno or 
returns an errno value. Instead, we should arrange for Haiku builds to 
use positive errno values, they way errno behaves on GNU and other 
POSIX-compatible hosts. This should be a much more maintainable solution.

Proposed patch attached.

0001-Improve-port-to-Haiku-errno-values.patch
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