On Wed, 16 Mar 2022 21:10:14 GMT, Tyler Steele <d...@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. > > Tyler Steele has refreshed the contents of this pull request, and previous > commits have been removed. The incremental views will show differences > compared to the previous content of the PR. The pull request contains one new > commit since the last revision: > > Addresses failure in NullClassTest on AIX. > > - Changes malloc(0) call to malloc(1) on AIX. p.s. this issue puts the finger on a sore point. We have corrected mallocs in the JDK in a number of places, e.g. in libverify: (https://github.com/openjdk/jdk/blob/3da5204b3c3a3f95bddcdcfe2628c2e0ed8a12d9/src/java.base/share/native/libverify/check_code.c#L91-L102) (which is also strictly speaking incorrect since the spec says to return a *non-unique* pointer). More generally, we have with AIX the problem that APIs have different behavior than the more usual nixes or are missing, and we need a porting layer to provide missing or change different APIs. Beside AIX-ish malloc, one example is dladdr, which is missing. In hotspot, we have os/aix, so we are fine. See `os/aix/hotspot/os/aix/porting_aix.cpp`. In the JDK I never found a good place for a porting layer, since the different JDK binaries don't have a common layer. So we have multiple versions of aix malloc and dladdr sprinkled across the libraries, which I always found embarrassing. (outside hotspot we implement dladdr at least in java.desktop/aix/native/libawt/porting_aix.c and java.base/aix/native/libjli/java_md_aix.c). If you find a way to commonize that code across JDK libraries, that would be cool. I even thought about providing a porting library completely independent from the OpenJDK itself, more like a system library. We did this for our internal iSeries port but the logistics were annoying, so we did not do it for AIX. But you at IBM may have a better idea. Cheers, Thomas ------------- PR: https://git.openjdk.java.net/jdk/pull/7829
