RFR: 8316907: Fix nonnull-compare warnings

[Daniel Jeliński]

On Tue, 26 Sep 2023 14:23:21 GMT, Daniel Jeliński <djelinski at openjdk.org> wrote:

> Please review this patch that fixes nonnull-compare warnings emitted by GCC after removing `-fno-delete-null-pointer-checks`.
> 
> The changes are pretty straightforward:
> - removal of `assert(this)` only changes the behavior of debug code; assertion failure in that place would result in a crash later on,
> - the check in `CodeBuffer::print` is a bit more complex to review; fortunately all uses except [`print_buf_locs`](https://github.com/openjdk/jdk/blob/1f7dfda7059f9dc14bff61b3c77d769ade85557d/src/hotspot/share/code/relocInfo.cpp#L990) are in CodeBuffer, and `print_buf_locs` is only used by developers from debugger.
> 
> I verified tier1-5 tests, just in case. No new failures.

Thanks for the reviews!

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PR Comment: https://git.openjdk.org/jdk/pull/15927#issuecomment-1742731754