[jboss-jira] [JBoss JIRA] (JASSIST-221) Got NPE when replacing a method in `instrument()`

[Goro Fuji (JIRA)]

     [ https://issues.jboss.org/browse/JASSIST-221?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Goro Fuji closed JASSIST-221.
-----------------------------

    Resolution: Incomplete Description


I'm sorry it might by my mistake. I can't reproduce this NPE anymore.

> Got NPE when replacing a method in `instrument()` 
> --------------------------------------------------
>
>                 Key: JASSIST-221
>                 URL: https://issues.jboss.org/browse/JASSIST-221
>             Project: Javassist
>          Issue Type: Bug
>    Affects Versions: 3.18.1-GA
>         Environment: JDK8 (build 1.8.0-b132) / Mac OSX 10.9.2
>            Reporter: Goro Fuji
>            Assignee: Shigeru Chiba
>
> I'm trying to modify some code in static initializer with {{m.replace("$_ = ($r)false;")}}, but I got NPE:
> {code}
> Caused by: java.lang.NullPointerException
> 	at javassist.bytecode.ConstPool.getMethodrefNameAndType(ConstPool.java:418)
> 	at javassist.expr.MethodCall.getNameAndType(MethodCall.java:43)
> 	at javassist.expr.MethodCall.getMethodName(MethodCall.java:107)
> 	at com.github.gfx.debugassert.DebugAssertPlugin$2.edit(DebugAssertPlugin.groovy:82)
> 	at javassist.expr.ExprEditor.loopBody(ExprEditor.java:192)
> 	at javassist.expr.ExprEditor.doit(ExprEditor.java:91)
> 	at javassist.CtBehavior.instrument(CtBehavior.java:712)
> 	at javassist.CtBehavior$instrument.call(Unknown Source)
> {code}
> I guess it is because the static initializer has no method name, but ClassPool expects a method (behavior) should have a name.
> ref. https://github.com/jboss-javassist/javassist/blob/master/src/main/javassist/bytecode/ConstPool.java#L418
> The NEP is thrown there: https://github.com/gfx/Gradle-DebugAssertPlugin/blob/master/buildSrc/src/main/groovy/com/github/gfx/debugassert/DebugAssertPlugin.groovy#L82-82
> (Currently I use a patched version of javassist which is stored in the repo, so the project works as expected.)
> {code}
> // line 77 at DebugAssertPlugin.groovy
> CtClass c = classPool.getCtClass(className)
> c.getClassInitializer()?.instrument(new ExprEditor() {
>     @Override
>     void edit(MethodCall m) throws CannotCompileException {
>         if (m.className == "java.lang.Class" && m.methodName == "desiredAssertionStatus") {
>             m.replace('{ $_ = ($r)true; }') // raises NPE!
>         }
>     }
> })
> {code}
> FYI, I have correct results with the following patch:
> {code}
> diff --git a/src/main/javassist/bytecode/ConstPool.java b/src/main/javassist/bytecode/ConstPool.java
> index f102421..9e62c89 100644
> --- a/src/main/javassist/bytecode/ConstPool.java
> +++ b/src/main/javassist/bytecode/ConstPool.java
> @@ -265,6 +265,9 @@ public final class ConstPool {
>       */
>      public int getNameAndTypeName(int index) {
>          NameAndTypeInfo ntinfo = (NameAndTypeInfo)getItem(index);
> +        if (ntinfo == null) {
> +            return 0;
> +        }
>          return ntinfo.memberName;
>      }
>  
> @@ -415,6 +418,9 @@ public final class ConstPool {
>       */
>      public int getMethodrefNameAndType(int index) {
>          MethodrefInfo minfo = (MethodrefInfo)getItem(index);
> +        if (minfo == null) {
> +            return 0;
> +        }
>          return minfo.nameAndTypeIndex;
>      }
>  
> @@ -635,6 +641,9 @@ public final class ConstPool {
>       */
>      public String getUtf8Info(int index) {
>          Utf8Info utf = (Utf8Info)getItem(index);
> +        if (utf == null) {
> +            return null;
> +        }
>          return utf.string;
>      }
> {code}



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