RFR: 8219810: javac throws NullPointerException [v3]

[Vicente Romero]

On Mon, 19 Dec 2022 15:44:57 GMT, Archie L. Cobbs <duke at openjdk.org> wrote:

>> JVMS 4.5 states:
>> 
>>> Each field of a class may have at most one of its ACC_PUBLIC, ACC_PRIVATE, and ACC_PROTECTED flags set (JLS §8.3.1), and must not have both its ACC_FINAL and ACC_VOLATILE flags set (JLS §8.3.1.4).
>> 
>> and JVMS 4.6 states:
>> 
>>> Each method of a class may have at most one of its ACC_PUBLIC, ACC_PRIVATE, and ACC_PROTECTED flags set (JLS §8.4.3). 
>> 
>> However, when reading class files these illegal combinations are not actually checked, and this can lead to compiler crashes as in the bug example.
>> 
>> This patch adds checks for these illegal combinations.
>
> Archie L. Cobbs has updated the pull request with a new target base due to a merge or a rebase. The incremental webrev excludes the unrelated changes brought in by the merge/rebase. The pull request contains four additional commits since the last revision:
> 
>  - Merge branch 'master' into JDK-8219810
>  - Merge branch 'master' into JDK-8219810
>  - Also disallow field access flags from having both FINAL and VOLATILE.
>  - Detect invalid access flag combinations for fields and methods in classfiles.

src/jdk.compiler/share/classes/com/sun/tools/javac/jvm/ClassReader.java line 2268:

> 2266: 
> 2267:         if (Integer.bitCount(rawFlags & (PUBLIC | PRIVATE | PROTECTED)) > 1)
> 2268:             throw badClassFile("illegal.flag.combo", String.format("0x%04x", (int)rawFlags), "method", m);

instead of: `String.format("0x%04x", (int)rawFlags)`, you could use method `com.sun.tools.javac.code.Flags::toString` which prints a string representation of the flags passed to it

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PR: https://git.openjdk.org/jdk/pull/10826