8224087: Compile C code for at least C99 Standard compliance

[zzambers]

This backport explicitly sets c99 standard for jdk c sources on compilers, where appropriate. Motivation for this is, recent gcc switch to c23 as default, causing errors (jdk sources are not c23 compatible).

Main problem is, that c23 no longer supports non-prototype function declarations (see (3) here). Example errors:

/mnt/ramdisk/java-11-openjdk-11.0.28.0.6-1.portable.jdk.el.x86_64.tarxz/src/src/java.base/unix/native/libnet/DefaultProxySelector.c:389:16: error: too many arguments to function 'g_proxy_resolver_lookup'; expected 0, have 4
  389 |     proxies = (*g_proxy_resolver_lookup)(resolver, uri, NULL, &error);
      |               ~^~~~~~~~~~~~~~~~~~~~~~~~~ ~~~~~~~~

/mnt/ramdisk/java-11-openjdk-11.0.28.0.6-1.portable.jdk.el.x86_64.tarxz/src/test/hotspot/jtreg/runtime/jsig/libTestJNI.c:45:22: error: assignment to 'void (*)(int,  siginfo_t *, void *)' from incompatible pointer type 'void (*)(void)' [-Wincompatible-pointer-types]
   45 |     act.sa_sigaction = (void (*)())sig_handler;
      |                      ^

There are more, if above are fixed. Non prototype function declarations are present even in newest jdk, but newer jdks have c standard set explicitly, so they do not cause errors there.

This should not increase minimum requirements for compiler toolchains needed to build jdk11. Jdk13, where this originates from, has same minimal compiler requirements as jdk11. ( gcc 4.8, clang 3.2, Xcode 8, Solaris Studio 12.4)

---

Progress

• Change must not contain extraneous whitespace
• Commit message must refer to an issue
• JDK-8224087 needs maintainer approval

Issue

• JDK-8224087: Compile C code for at least C99 Standard compliance (Enhancement - P4 - Approved)

Reviewers

• Andrew John Hughes (@gnu-andrew - Reviewer)

Reviewing

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[bridgekeeper]

👋 Welcome back zzambers! A progress list of the required criteria for merging this PR into master will be added to the body of your pull request. There are additional pull request commands available for use with this pull request.

[openjdk]

@zzambers This change now passes all automated pre-integration checks.

After integration, the commit message for the final commit will be:

8224087: Compile C code for at least C99 Standard compliance

Reviewed-by: andrew

You can use pull request commands such as /summary, /contributor and /issue to adjust it as needed.

At the time when this comment was updated there had been 4 new commits pushed to the master branch:

• 26a8aca: 8354941: Build failure with glibc 2.42 due to uabs() name collision
• 465fb7d: 8359402: Test CloseDescriptors.java should throw SkippedException when there is no lsof/sctp
• 43b28ee: 8364597: Replace THL A29 Limited with Tencent
• ... and 1 more: https://git.openjdk.org/jdk11u-dev/compare/2c32878f38c7078ce16079eda53a3ab6627aa489...master

As there are no conflicts, your changes will automatically be rebased on top of these commits when integrating. If you prefer to avoid this automatic rebasing, please check the documentation for the /integrate command for further details.

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[openjdk]

This backport pull request has now been updated with issue from the original commit.

[mlbridge]

Webrevs

• 00: Full (e7e9318a)

[gnu-andrew]

I'm in two minds about this. Specifying the standard explicitly is the right thing to do (I added similar for C++ years back) but we could just make that C90 so as to not raise older compilers.

I think, given some compilers have been defaulting to C99 for some time anyway (and maybe even later), this should be safe and may avoid problems with future backports. Let's get it in early and ensure it is well tested before January.

What compilers have you tested this change with?

[zzambers]

I was also thinking, whether c99 is ok here, but given that jdk13 has same minimum compiler versions, it should be safe.

Apart from testing in GHA. I tested these compiler versions (WORK):

• gcc-15.2.1 (f42; original motivation for this backport)
• gcc-4.8.5 (rhel-7)
• clang-3.8.1 (debian stretch)

Minimum accepted versions are gcc-4.8 and clang 3.2, so I tried to get close to that, based on what is available in old rhel/debian, not building my own toolchain. (Debian Jessie has clang 3.5, but that one (clang) was segfaulting during the build even on master, and Wheezy has clang 3.0)
(builds needed to disable warnings as errors, but that was same for master (and warnings seem the same))

For msvc there should be no change in compiler flags by this backport.

When it comes to Solaris, I could not test build there, because I don't have that OS available to me. But given that some awt libraries were already compiled with c99 flags, compiler flags should work.

[zzambers]

Build logs:
jdk-c99-logs.tar.gz

[gnu-andrew]

Thanks. My main concern was less what is claimed to be supported and more what people are actively building on at present. In particular, I'm reassured that it still builds on RHEL 7 as that's the one of most importance to us and where I test each build promotion.

I think the Solaris change, while untested, should be safe as it essentially just widens the scope of the existing usage from awt to the whole library build. My concern was the new option.

I think this is good to go in and should then get plenty of testing before January's release.

[gnu-andrew]

/approve yes

[openjdk]

@gnu-andrew
8224087: The approval request has been approved.

[vieiro]

Confirmed this builds on rhel7 with gcc8.

[zzambers]

/integrate

[openjdk]

@zzambers
Your change (at version e7e9318) is now ready to be sponsored by a Committer.

[jerboaa]

/sponsor

[openjdk]

Going to push as commit 156d998.
Since your change was applied there have been 4 commits pushed to the master branch:

• 26a8aca: 8354941: Build failure with glibc 2.42 due to uabs() name collision
• 465fb7d: 8359402: Test CloseDescriptors.java should throw SkippedException when there is no lsof/sctp
• 43b28ee: 8364597: Replace THL A29 Limited with Tencent
• ... and 1 more: https://git.openjdk.org/jdk11u-dev/compare/2c32878f38c7078ce16079eda53a3ab6627aa489...master

Your commit was automatically rebased without conflicts.

[openjdk]

@jerboaa @zzambers Pushed as commit 156d998.

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