[crac] RFR: 8368929: [CRaC] Move CPUFeatures check to C/R engine

[Jan Kratochvil]

On Tue, 30 Sep 2025 13:17:54 GMT, Radim Vansa <rvansa at openjdk.org> wrote:

> Right now the logic checking if CPU features used before checkpoint match current CPU features is in VM code. VM stores and retrieves CPU features through C/R API's user_data extension. This is convenient when we have a single image that can be either accepted or rejected, but does not offer the flexibility for C/R engine to select the best image for current execution environment.
> 
> The goal of this issue is to move to a declarative API that will express the requirements using more abstract means, labels (for CPU architecture) and bitmaps (for CPU features).

src/java.base/share/native/libcrexec/image_constraints.cpp line 155:

> 153:     assert(eq < nl);
> 154:     if (!strncmp(line, LABEL_PREFIX, strlen(LABEL_PREFIX))) {
> 155:       Tag& t = tags.add({

/home/runner/work/crac/crac/src/java.base/share/native/libcrexec/image_constraints.cpp:155:12: error: unused variable ‘t’ [-Werror=unused-variable]

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PR Review Comment: https://git.openjdk.org/crac/pull/266#discussion_r2393841228