Integrated: 8283225: ClassLoader.c produces incorrect OutOfMemory Exception when length is 0 (aix)

[Tyler Steele]

On Tue, 15 Mar 2022 22:58:48 GMT, Tyler Steele <duke at openjdk.java.net> wrote:

> As described in the linked issue, NullClassBytesTest fails due an OutOfMemoryError produced on AIX when the test calls defineClass with a byte array of size of 0. The native implementation of defineClass then calls  malloc with a size of 0. On AIX malloc(0) returns NULL, while on other platforms it return a valid address. When NULL is produced by malloc for this reason, ClassLoader.c incorrectly interprets this as a failure due to a lack of memory.
> 
> ~~This PR modifies ClassLoader.c to produce an OutOfMemoryError only when `errno == ENOMEM` and to produce a ClassFormatError with the message "ClassLoader internal allocation failure" in all other cases (in which malloc returns NULL).~~ [edit: The above no longer describes the PR's proposed fix. See discussion below]
> 
> In addition, I performed some minor tidy-up work in ClassLoader.c by changing instances of `return 0` to `return NULL`, and `if (some_ptr == 0)` to `if (some_ptr == NULL)`. This was done to improve the clarity of the code in ClassLoader.c, but didn't feel worthy of opening a separate issue.
> 
> ### Alternatives
> 
> It would be possible to address this failure by modifying the test to accept the OutOfMemoryError on AIX. I thought it was a better solution to modify ClassLoader.c to produce an OutOfMemoryError only when the system is actually out of memory.
> 
> ### Testing
> 
> This change has been tested on AIX and Linux/x86.

This pull request has now been integrated.

Changeset: cab4ff64
Author:    Tyler Steele <tyler.steele at ibm.com>
Committer: Thomas Stuefe <stuefe at openjdk.org>
URL:       https://git.openjdk.java.net/jdk/commit/cab4ff64541393a974ea91e35167668ef0036804
Stats:     11 lines in 1 file changed: 11 ins; 0 del; 0 mod

8283225: ClassLoader.c produces incorrect OutOfMemory Exception when length is 0 (aix)

Reviewed-by: stuefe, rriggs, dholmes

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PR: https://git.openjdk.java.net/jdk/pull/7829