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From: Florian Weimer <fweimer@redhat.com>
To: Gioele Barabucci via Systemtap <systemtap@sourceware.org>
Cc: Gioele Barabucci <gioele@svario.it>
Subject: Re: [PATCH] dtrace: Use deterministic temp file creation for all
 temp files
References: <6bfff40c-2c4b-c119-116d-7834310299d7@svario.it>
Date: Mon, 27 Feb 2023 16:49:06 +0100
In-Reply-To: <6bfff40c-2c4b-c119-116d-7834310299d7@svario.it> (Gioele
	Barabucci via Systemtap's message of "Mon, 27 Feb 2023 13:13:16
	+0100")
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* Gioele Barabucci via Systemtap:

> +def mktemp_determ(sources, suffix):
> +    # for reproducible-builds purposes, use a predictable tmpfile path
> +    sha = hashlib.sha256()
> +    for source in sources:
> +        sha.update(source.encode('utf-8'))
> +    fname = ".dtrace-temp." + sha.hexdigest()[:8] + suffix
> +    tries = 0
> +    while True:
> +        tries += 1
> +        if tries > 100: # if file exists due to previous crash or whatever
> +            raise Exception("cannot create temporary file \""+fname+"\"")
> +        try:
> +            wxmode = 'x' if sys.version_info > (3,0) else 'wx'
> +            fdesc = open(fname, mode=wxmode)
> +            break
> +        except FileExistsError:
> +            time.sleep(0.1) # vague estimate of elapsed time for concurrent identical gcc job
> +            pass # Try again
> +
> +    return fdesc, fname

This looks like creating a file with a suitable name may block forward
progress indefinitely?  Like from a previous crash of the tool?

It might be more robust to use a dedicated temporary directory and a
predictable file name under that directory.

Thanks,
Florian