8367282: FORBID_C_FUNCTION needs exception spec consistent with library declaration #27180

kimbarrett · 2025-09-10T02:58:31Z

Please review this change to FORBID_C_FUNCTION to make the exception specs of
the forbidding declarations match up with the exception specs of the
associated library declarations. This needs to account for different platform
libraries either having or not having exception specs. It's needed because,
after switching to C++17, some compilers complain about some differences in
the exception specs.

Also removed the workaround for JDK-8367051, which should no longer be needed
after this change.

Hoping someone will test the aix-ppc port. @MBaesken or @TheRealMDoerr ?

Testing: mach5 tier1, GHA sanity checks (nearly finished)
Locally (linux-aarch64) built with clang, which failed without the JDK-8367051
workaround.

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Change must be properly reviewed (1 review required, with at least 1 Reviewer)
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Issue

JDK-8367282: FORBID_C_FUNCTION needs exception spec consistent with library declaration (Enhancement - P4)

Reviewers

David Holmes (@dholmes-ora - Reviewer)
Matthias Baesken (@MBaesken - Reviewer)

Reviewing

Using git

Checkout this PR locally:
$ git fetch https://git.openjdk.org/jdk.git pull/27180/head:pull/27180
$ git checkout pull/27180

Update a local copy of the PR:
$ git checkout pull/27180
$ git pull https://git.openjdk.org/jdk.git pull/27180/head

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Checkout this PR locally:
$ git pr checkout 27180

View PR using the GUI difftool:
$ git pr show -t 27180

Using diff file

Download this PR as a diff file:
https://git.openjdk.org/jdk/pull/27180.diff

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bridgekeeper · 2025-09-10T03:00:14Z

👋 Welcome back kbarrett! 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 · 2025-09-10T03:01:25Z

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

ℹ️ This project also has non-automated pre-integration requirements. Please see the file CONTRIBUTING.md for details.

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

8367282: FORBID_C_FUNCTION needs exception spec consistent with library declaration

Reviewed-by: dholmes, mbaesken

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 60 new commits pushed to the master branch:

aeffce7: 8367271: Add parsing tests to DateFormat JMH benchmark
44aad07: 8328874: Class::forName0 should validate the class name length early
10fea86: 8367371: Remove @requires vm.opt.UseLargePages from InternSharedString.java test
... and 57 more: https://git.openjdk.org/jdk/compare/cc6d34b2fa299a68a05e65e25c1f41dffa67c118...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.

➡️ To integrate this PR with the above commit message to the master branch, type /integrate in a new comment.

openjdk · 2025-09-10T03:02:17Z

@kimbarrett The following label will be automatically applied to this pull request:

hotspot

When this pull request is ready to be reviewed, an "RFR" email will be sent to the corresponding mailing list. If you would like to change these labels, use the /label pull request command.

mlbridge · 2025-09-10T03:05:55Z

Webrevs

01: Full - Incremental (52f28437)
00: Full (0fcb5f53)

dholmes-ora

Seems reasonable. Thanks for getting this sorted out.

MBaesken · 2025-09-10T07:52:01Z

src/hotspot/share/utilities/compilerWarnings.hpp


-#define FORBID_NORETURN_C_FUNCTION(Signature, Alternative) \
-  FORBID_C_FUNCTION(FORBIDDEN_FUNCTION_NORETURN_ATTRIBUTE Signature, Alternative)
+#define FORBID_NORETURN_C_FUNCTION(Signature, Noexcept, Alternative)    \


Is the added whitespace after ')' intended ?

Thanks for noticing. Will fix.

MBaesken · 2025-09-10T08:18:50Z

Bad news from AIX, with this patch included we get build errors like this

=== Output from failing command(s) repeated here ===
* For target hotspot_variant-server_libjvm_objs_sharedRuntimeTrans.o:
In file included from /jdk/src/hotspot/share/runtime/sharedRuntimeTrans.cpp:26:
In file included from /jdk/src/hotspot/share/runtime/interfaceSupport.inline.hpp:31:
In file included from /jdk/src/hotspot/share/gc/shared/gc_globals.hpp:28:
In file included from /jdk/src/hotspot/share/runtime/globals_shared.hpp:28:
In file included from /jdk/src/hotspot/share/utilities/align.hpp:31:
In file included from /jdk/src/hotspot/share/utilities/globalDefinitions.hpp:31:
/jdk/src/hotspot/share/utilities/forbiddenFunctions.hpp:61:23: error: exception specification in declaration does not match previous declaration
   61 | FORBID_C_FUNCTION(int sprintf(char*, const char*, ...), noexcept, "use os::snprintf");
      |                       ^
/usr/include/stdio.h:325:12: note: previous declaration is here
  325 | extern int      sprintf(char *__restrict__, const char *__restrict__, ...); 
      |                 ^

snake66 · 2025-09-10T09:49:54Z

Tested and found to work on FreeBSD Aarch64 (with all my still out-of-tree patches applied.)

MBaesken · 2025-09-10T12:21:27Z

Seems the forbidden sprintf AND snprintf cause the trouble on AIX, if I uncomment those 2 from forbiddenFunctions.hpp on top of this patch

/*
FORBID_C_FUNCTION(int sprintf(char*, const char*, ...), noexcept, "use os::snprintf");
FORBID_C_FUNCTION(int snprintf(char*, size_t, const char*, ...), noexcept, "use os::snprintf");
*/

the rest of forbidden functions causes no trouble on AIX, the build is successful.

kimbarrett · 2025-09-10T20:16:15Z

Tested and found to work on FreeBSD Aarch64 (with all my still out-of-tree patches applied.)

Thanks for checking that!

kimbarrett · 2025-09-10T20:19:20Z

Seems the forbidden sprintf AND snprintf cause the trouble on AIX, [...] the rest of forbidden functions causes
no trouble on AIX, the build is successful.

I was afraid something like this might turn up. I can hack around the
sprintf/snprintf AIX issue. But I think the only reliable long-term solution
might be to generate the forbidding declarations as part of the build process.
That's more work than I want to do for this right now though.

dholmes-ora · 2025-09-11T05:54:14Z

src/hotspot/share/utilities/compilerWarnings.hpp

@@ -119,8 +119,10 @@
  extern "C" {                                                  \
    [[deprecated(Alternative)]]                                 \
    Signature                                                   \
-    /* Not PASTE_TOKENS, which expands FFCN => nothing. */      \
-    FORBIDDEN_FUNCTION_COND_NOEXCEPT_ ## Noexcept               \
+    /* 2-step pasting to avoid expansion of FFCN => nothing. */ \


Was this an issue with AIX or is this just a "better" way?

This is needed in order to allow NOT_AIX(noexcept) for the Noexcept
argument. We need pasting of the expansion, not direct pasting. Just using
direct ## as before results in making something like
FORBIDDEN_FUNCTION_COND_NOEXCEPT_NOT_AIX(noexcept)
which isn't what we want here. And doing a single paste, e.g.
PASTE_TOKENS(FORBIDDEN_FUNCTION_COND_NOEXCEPT_, Noexcept)
expands the first argument to nothing, so we just get noexcept, which isn't
what we want and doesn't work on platforms that don't declare their library
functions noexcept. The joys of macros...

MBaesken

Works now on AIX as well, thanks !

kimbarrett · 2025-09-12T18:55:27Z

Thanks for reviews @MBaesken and @dholmes-ora

kimbarrett · 2025-09-12T18:55:35Z

/integrate

openjdk · 2025-09-12T18:57:16Z

Going to push as commit 4e59c63.
Since your change was applied there have been 62 commits pushed to the master branch:

850f904: 8367451: GenShen: Remove the option to compute age census during evacuation
11df289: 8367378: GenShen: Missing timing stats when old mark buffers are flushed during final update refs
aeffce7: 8367271: Add parsing tests to DateFormat JMH benchmark
... and 59 more: https://git.openjdk.org/jdk/compare/cc6d34b2fa299a68a05e65e25c1f41dffa67c118...master

Your commit was automatically rebased without conflicts.

openjdk · 2025-09-12T18:57:23Z

@kimbarrett Pushed as commit 4e59c63.

💡 You may see a message that your pull request was closed with unmerged commits. This can be safely ignored.

kimbarrett added 2 commits September 9, 2025 22:23

add noexcept

749ebeb

remove JDK-8367051 workaround

0fcb5f5

openjdk bot added hotspot [email protected] rfr Pull request is ready for review labels Sep 10, 2025

dholmes-ora approved these changes Sep 10, 2025

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openjdk bot added the ready Pull request is ready to be integrated label Sep 10, 2025

MBaesken reviewed Sep 10, 2025

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work around AIX noexcept inconsistencies

52f2843

openjdk bot removed the ready Pull request is ready to be integrated label Sep 11, 2025

dholmes-ora reviewed Sep 11, 2025

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dholmes-ora approved these changes Sep 12, 2025

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openjdk bot added the ready Pull request is ready to be integrated label Sep 12, 2025

MBaesken approved these changes Sep 12, 2025

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openjdk bot closed this Sep 12, 2025

openjdk bot removed ready Pull request is ready to be integrated rfr Pull request is ready for review labels Sep 12, 2025

kimbarrett deleted the clang-forbid-noexcept branch September 12, 2025 18:57

8367282: FORBID_C_FUNCTION needs exception spec consistent with library declaration #27180

8367282: FORBID_C_FUNCTION needs exception spec consistent with library declaration #27180

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