RFR: 8352251: Implement JEP 518: JFR Cooperative Sampling [v32]

[Aleksey Shipilev]

On Wed, 21 May 2025 11:10:44 GMT, Markus Grönlund <mgronlun at openjdk.org> wrote:

> > I am taking a look how to unbreak Minimal and Zero again.
> 
> Hmm. I thought JFR was not defined for Zero?

Yes. But there is an instance of the fairly common `#if` vs `#ifdef` trap here:


diff --git a/src/hotspot/share/runtime/safepointMechanism.cpp b/src/hotspot/share/runtime/safepointMechanism.cpp
index 57fbc9078c8..d4160161f19 100644
--- a/src/hotspot/share/runtime/safepointMechanism.cpp
+++ b/src/hotspot/share/runtime/safepointMechanism.cpp
@@ -32,7 +32,7 @@
 #include "runtime/safepointMechanism.inline.hpp"
 #include "runtime/stackWatermarkSet.hpp"
 #include "utilities/globalDefinitions.hpp"
-#ifdef INCLUDE_JFR
+#if INCLUDE_JFR
 #include "jfr/jfr.inline.hpp"
 #endif


"No JFR" is `#define INCLUDE_JFR 0`. Which means `#if INCLUDE_JFR` == `false`, but `#ifdef INCLUDE_JFR` == `true`.

The patch above fixes both Minimal and Zero Hotspot fastdebug builds for me locally. I am running full builds now.

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PR Comment: https://git.openjdk.org/jdk/pull/24296#issuecomment-2897565909