RFR: 8374521: Support fine-grained native debug levels

[Kerem Kat]

On Tue, 6 Jan 2026 08:28:35 GMT, Aleksey Shipilev <shade at openjdk.org> wrote:

> [JDK-8374507](https://bugs.openjdk.org/browse/JDK-8374507) forced me to look into debug info sizes again. And I remembered that GCC actually have debug-level support, which can select what kind of diagnostic data is in the debug info. See: https://gcc.gnu.org/onlinedocs/gcc-4.5.0/gcc/Debugging-Options.html
> 
> Allowing users to configure the debug level allows two major deviations from the default level (2):
>  level=1: significantly reduce the debug info size, but still allow backtrace reconstruction
>  level=3: add even more debugging info, like macro expansion, into the debug data
> 
> This RFE upstreams the variant the patch that I have been using in builds.shipilev.net binaries: the fastdebug variants there are done with GCC level=1, greatly optimizing the debug binary sizes, while still maintaining the major benefit of debug binaries -- rich crash diagnostics.
> 
> I threw in this option into current GHA builds to conserve more disk space on runners and/or transfers. 
> 
> I am open for bikeshedding on the option name :)

make/autoconf/flags-cflags.m4 line 72:

> 70:   DEBUG_PREFIX_CFLAGS=
> 71: 
> 72:   UTIL_ARG_WITH(NAME: fine-debug-level, TYPE: string,

How about `debug-info-level`?

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PR Review Comment: https://git.openjdk.org/jdk/pull/29056#discussion_r2665018759