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Re: C99 compliance for src/port/snprintf.c

Andres Freund <andres@anarazel.de>

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From: Andres Freund <andres@anarazel.de>
To: Thomas Munro <thomas.munro@enterprisedb.com>
Cc: Tom Lane <tgl@sss.pgh.pa.us>, David Steele <david@pgmasters.net>, PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>
Date: 2018-08-15T23:06:13Z
Lists: pgsql-hackers 
Hi,

On 2018-08-16 10:54:01 +1200, Thomas Munro wrote:
> Really?  I am not an MSVC user but I had the impression that their C
> mode (/TC or files named .c) was stuck on C89/C90 as a matter of
> policy, as Herb Sutter explained here (though maybe the situation has
> changed since then):

They revised their position gradually, starting soon after. They claim
full C99 "language" (vs library, which is also pretty complete)
compliance now.  I've not yet bothered to fully figure out which version
supports what however.  Nor am I really sure about the whole flag thing,
it appears there's a gui element to choose, which we might need to mirror on
the xml level.

A bit of googling shows
https://docs.microsoft.com/en-us/previous-versions/visualstudio/visual-studio-2013/hh409293(v=vs.120)
"
Supports these ISO C99 language features:

    _Bool

    Compound literals.

    Designated initializers.

    Mixing declarations with code.
"

which I think is what we roughly would want.  So it looks like msvc 2013
might be the relevant requirement.


> That's presumably why cfbot's appveyor build always complains about
> people declaring variables after statements.

IIRC even in older versions there's a flag to allow that.


> To allow that particular language feature, it looks like you have to
> tell it that your .c file is really a C++ program with /TP.  But that
> opens a separate can of worms, doesn't it?

Yea, I don't think we want to go there by default soon.

Greetings,

Andres Freund

Commits

Same data as JSON: GET /api/v1/messages/:b64id/commits the thread's linked commits as JSON, with link sources. API reference →

  1. Remove test for VA_ARGS, implied by C99.

  2. Introduce minimal C99 usage to verify compiler support.

  3. Require C99 (and thus MSCV 2013 upwards).

  4. Require a C99-compliant snprintf(), and remove related workarounds.

  5. Try to enable C99 in configure, but do not rely on it (yet).

  6. Make snprintf.c follow the C99 standard for snprintf's result value.

  7. Clean up assorted misuses of snprintf()'s result value.