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To: 9front@9front.org
Subject: Re: [9front] libmp and error handling
Date: Sat, 24 Oct 2020 18:52:53 -0500
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X-Bullshit: injection proxy YAML callback shader-aware engine 

> This is still likely to require quite a bit of change in libmp; if
> it's currently calling sysfatal, then it's very likely full of
> things like:
> 
> 	x = a();
> 	y = b()
> 	return mpadd(x, y);
> 
> which means that if b() errors, then x is leaked.

So, I tried changing libmp itself.  It rapidly became a hairy mess of
return checking, and making the library do more allocation just to
preserve the original function arguments.  Instead, here's a patch to
fix the manpage:

diff -r 5a6b0e6ac3b2 sys/man/2/mp
--- a/sys/man/2/mp	Sun Oct 25 00:49:29 2020 +0200
+++ b/sys/man/2/mp	Sat Oct 24 18:51:53 2020 -0500
@@ -287,8 +287,8 @@
 .I mpnew
 and
 .IR mpcopy ,
-will return
-.B nil
+will call sysfatal (see
+.IR perror (2))
 if the allocation fails.
 .PP
 Input and result parameters may point to the same