RFR: 8264593: debug.cpp utilities should be available in product builds. [v2]

[Kevin Walls]

On Tue, 27 Apr 2021 16:57:18 GMT, Kevin Walls <kevinw at openjdk.org> wrote:

>> This is a pull request to move the ifndef PRODUCT in src/hotspot/share/utilities/debug.cpp, and add JNIEXPORT for symbol visibility on Windows.
>> 
>> With these changes, we can use gdb on a live Linux process of a product build JVM, and call debug.cpp utilities.
>> e.g. "call universe()", or "call hsfind(0xADDRESS)".
>> 
>> (I found that making calls in the JLI_Launch thread (gdb's thread 1) will crash, but switching first to a JavaThread works.)
>> 
>> In Visual Studio use the Immediate window, just type the function name.  Verified that without the changes, the symbols can't be seen/called.
>> 
>> Printing happens on the LIVE jvm's tty (not the gdb session).
>> 
>> 
>> WizardMode is a develop flag, can't be changed in a product build, so avoid changing that in the debug() utility.
>> 
>> 
>> pa() is left ifndef PRODUCT, as the class AllocatedObj is ifndef PRODUCT in src/hotspot/share/memory/allocation.hpp
>> 
>> 
>> pns(...) uses frame fr(sp, fp, pc); but we have an ifndef PRODUCT on frame constructor:  frame(void* sp, void* fp, void* pc);
>> Leave pns and pns2 ifndef PRODUCT.
>> 
>> 
>> File size changes:
>> Linux: libjvm.so becomes 8904 bytes larger.
>> Windows: jvm.dll becomes 6656 bytes larger.
>
> Kevin Walls has updated the pull request with a new target base due to a merge or a rebase. The incremental webrev excludes the unrelated changes brought in by the merge/rebase. The pull request contains three additional commits since the last revision:
> 
>  - Merge remote-tracking branch 'upstream/master' into debug_utils
>  - Remove pa() util as unnecessary.  Tidy help.
>  - 8264593: debug.cpp utilities should be available in product builds.

Thanks all.  The main limit with product builds is that printing Java object details e.g. with hsfind() doesn't include full field information, though it's still useful.  Plan to consider that separately.

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PR: https://git.openjdk.java.net/jdk/pull/3307