Re: stopgap fix for signal handling during restore_command

On Tue, Feb 28, 2023 at 08:36:03PM -0800, Nathan Bossart wrote:
> On Sun, Feb 26, 2023 at 12:12:27PM -0800, Andres Freund wrote:
>> Partially I just want something that can easily be searched for, that can have
>> comments attached to it documenting why what it is doing is safe.
>>
>> It'd not be a huge amount of work to have a slow and restricted string
>> interpolation support, to make it easier to write messages. Converting floats
>> is probably too hard to do safely, and I'm not sure %m can safely be
>> supported. But basic things like %d would be pretty simple.
>>
>> Basically a loop around the format string that directly writes to stderr using
>> write(), and only supports a signal safe subset of normal format strings.
>
> Got it, thanks. I will try to put something together along these lines,
> although I don't know if I'll pick up the interpolation support in this
> thread.

Here is an attempt at adding a signal safe function for writing to STDERR.

I didn't add support for format strings, but looking ahead, I think one
challenge will be avoiding va_start() and friends. In any case, IMO format
string support probably deserves its own thread.

--
Nathan Bossart
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