Re: RFR: 8224087: Compile C code for at least C99 Standard compliance

[David Holmes]

Hi Thomas,

On 21/05/2019 1:45 pm, Thomas Stüfe wrote:
Hi David,
Thank you for doing this, this looks all very good.

Thanks for taking another look.

I wish though we had a clear whitelist of features to use or blacklist 
for features to avoid. Most developers do not use Windows as a primary 
platform, so it will always be a surprise whether Windows breaks in 
submit tests.

I agree. Unfortunately MS don't even do a good job of documenting their 
supported extensions to C89/90 - AFAICS they don't list for-loop 
declaration expressions.

I am also (a bit) concerned about C99 features creeping in which would 
prevent verbatim backporting of patches to older releases. But let’s see 
if that is really a problem in practice.

Yes lets not try to solve problems that haven't arisen yet. 11u at least 
should be in a position to enforce the same use of C99.

Thanks,
David


Thanks, Thomas


On Tue 21. May 2019 at 02:58, David Holmes <david.hol...@oracle.com 
<mailto:david.hol...@oracle.com>> wrote:

    Thank you everyone for taking a look at this.

    Here is version 2:

    http://cr.openjdk.java.net/~dholmes/8224087/webrev.v2/

    Changes:
    - set c99 rather than gnu99
    - Volker's change for xlc to match gcc and clang
    - added short note to build doc (can do wiki later)
    - cosmetic change of name to make variable based on other feedback
    during the C++14 discussion

    Thanks,
    David

    On 20/05/2019 5:40 pm, David Holmes wrote:
     > Bug: https://bugs.openjdk.java.net/browse/JDK-8224087
     > webrev: http://cr.openjdk.java.net/~dholmes/8224087/webrev/
     >
     > The need to remove a for-loop declaration expression to appease
    gcc 4.8
     > annoyed me enough to investigate setting C99 as our minimum allow
     > C-language level when compiling. It turned out to be a lot more
    complex
     > a situation than I thought due to toolchain quirks. See lots of
    details
     > in the bug report.
     >
     > To summarise the changes:
     > - gcc: force to -std=gnu99
     > - clang force to -std=gnu99
     > - Solaris studio - no effective change
     > - Visual Studio - no change
     > - xlc - no effective change (but we use the explicit flag rather
    than
     > accepting it as default)
     >
     > I've checked how this works with all the toolchains except xlc as
    I have
     > no access to that. Some assistance from someone who can verify the
     > correctness on xlc would be appreciated.
     >
     > Thanks,
     > David