Attachment 279655 Details for Bug 544943 – Debugging Notes

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Debugging Notes

file_544943.txt (text/plain), 6.91 KB, created by Manoj N Palat

on 2019-08-21 23:26:04 EDT

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Creator: Manoj N Palat

Created: 2019-08-21 23:26:04 EDT

Size: 6.91 KB

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obsolete

>Debugging notes: 
>For the following code snippet,
>
>  public static int foo(int i) throws Exception {
>    int v = switch (i) {
>        case 0 -> switch (i) {
>              case 0 -> 0;
>              default -> throw new Exception();
>            };
>        default -> 0;
>    };
>    return v;
>  }
>
>The code generated is shown below:
>// Method descriptor #15 (I)I
>  // Stack: 3, Locals: 1
>  public static int foo(int arg0) throws java.lang.Exception;
>     0  new java.lang.Error [23]
>     3  dup
>     4  ldc <String "Unresolved compilation problem: \n"> [25]
>     6  invokespecial java.lang.Error(java.lang.String) [27]
>     9  athrow
>      Line numbers:
>        [pc: 0, line: 3]
>
>The message at runtime is of course given by the line 4  ldc <String "Unresolved compilation problem: \n"> which is inserted into the code stream by the following st (debug breakpoint):
>ClassFile.addProblemMethod(AbstractMethodDeclaration, MethodBinding, CategorizedProblem[]) line: 914	
>ClassFile.addProblemMethod(AbstractMethodDeclaration, MethodBinding, CategorizedProblem[], int) line: 952	
>MethodDeclaration(AbstractMethodDeclaration).generateCode(ClassScope, ClassFile) line: 317	
>TypeDeclaration.generateCode(ClassFile) line: 583	
>TypeDeclaration.generateCode(CompilationUnitScope) line: 653	
>CompilationUnitDeclaration.generateCode() line: 410	
>CompilationUnitResolver.resolve(CompilationUnitDeclaration, ICompilationUnit, NodeSearcher, boolean, boolean, boolean) line: 1249	
>CompilationUnitResolver.resolve(ICompilationUnit, IJavaProject, List, NodeSearcher, Map, WorkingCopyOwner, int, IProgressMonitor) line: 714	
>ASTParser.internalCreateAST(IProgressMonitor) line: 1221	
>ASTParser.createAST(IProgressMonitor) line: 836	
>CoreASTProvider$1.run() line: 271	
>This code path is taken due to Boolean check on abort (a Boolean variable) at MethodDeclaration(AbstractMethodDeclaration).generateCode(ClassScope, ClassFile) line: 317	
>
>The variable abort is true because of a throw of AbortMethod at:
>ClassFile.traverse(MethodBinding, int, byte[], int, int, Map, boolean) line: 5842	
>ClassFile.generateStackMapTableAttribute(MethodBinding, int, int, int, boolean) line: 4804	
>ClassFile.completeCodeAttribute(int) line: 1513	
>MethodDeclaration(AbstractMethodDeclaration).generateCode(ClassFile) line: 357	
>MethodDeclaration(AbstractMethodDeclaration).generateCode(ClassScope, ClassFile) line: 281	
>TypeDeclaration.generateCode(ClassFile) line: 583	
>TypeDeclaration.generateCode(CompilationUnitScope) line: 653	
>CompilationUnitDeclaration.generateCode() line: 410	
>CompilationUnitProblemFinder(Compiler).resolve(CompilationUnitDeclaration, ICompilationUnit, boolean, boolean, boolean) line: 1070	
>CompilationUnitProblemFinder(Compiler).resolve(ICompilationUnit, boolean, boolean, boolean) line: 1106	
>CompilationUnitProblemFinder.process(CompilationUnit, SourceElementParser, WorkingCopyOwner, HashMap, boolean, int, IProgressMonitor) line: 280	
>CompilationUnitProblemFinder.process(CompilationUnit, WorkingCopyOwner, HashMap, boolean, int, IProgressMonitor) line: 346	
>Interesting variables at generateStackMapTableAttribute call â maxLocals:2
>Variable values/opcodes: 
>
>frame added (total : 1)
>106: iload_3
>107: tableswitch
>frame added (total : 2)
>
>125: iload_3
>[pc : -1 locals: 1 stack items: 1
>locals: [I,top]
>stack: [I]
>]
>
>
>126: tableswitch
>[pc : -1 locals: 1 stack items: 0
>locals: [I,top]
>stack: []
>]
>
>
>Frame added: - frames:
>{-1=[pc : -1 locals: 1 stack items: 0
>locals: [I,top]
>stack: []
>], 20=[pc : 20 locals: 1 stack items: 0
>locals: [I,top]
>stack: []
>], 40=[pc : 40 locals: 1 stack items: 0
>locals: [I,top]
>stack: []
>]}
>
>
>145: iconst_0
>[pc : -1 locals: 1 stack items: 1
>locals: [I,top]
>stack: [I]
>]
>
>[pc : -1 locals: 1 stack items: 0
>locals: [I,top]
>stack: []
>]
>146: goto
>realjumpTarget: [-1, 52, 20, 53, 40, 44]
>
>
>149: new
>[pc : -1 locals: 1 stack items: 1
>locals: [I,top]
>stack: [uninitialized(java/lang/Exception)]
>]
>
>
>152: dup
>[pc : -1 locals: 1 stack items: 2
>locals: [I,top]
>stack: [uninitialized(java/lang/Exception),uninitialized(java/lang/Exception)]
>]
>
>153: invokespecial
>(init)
>[pc : -1 locals: 1 stack items: 1
>locals: [I,top]
>stack: [java/lang/Exception]
>]
>
>156: throw 
>[pc : -1 locals: 1 stack items: 0
>locals: [I,top]
>stack: []
>]
>realJumpTarget: [-1, 52, 20, 53, 40, 44]
>
>frames: {-1=[pc : -1 locals: 1 stack items: 0
>locals: [I,top]
>stack: []
>], 20=[pc : 20 locals: 1 stack items: 0
>locals: [I,top]
>stack: []
>], 40=[pc : 40 locals: 1 stack items: 0
>locals: [I,top]
>stack: []
>], 44=[pc : 44 locals: 1 stack items: 0
>locals: [I,top]
>stack: []
>]}
>
>for frame = 
>[pc : -1 locals: 1 stack items: -1
>locals: [I,top]
>stack: []
>]
>then at the st:
>StackMapFrame.duplicate() line: 129	
>ClassFile.traverse(MethodBinding, int, byte[], int, int, Map, boolean) line: 5955	
>ClassFile.generateStackMapTableAttribute(MethodBinding, int, int, int, boolean) line: 4804	
>ClassFile.completeCodeAttribute(int) line: 1513	
>MethodDeclaration(AbstractMethodDeclaration).generateCode(ClassFile) line: 357	
>MethodDeclaration(AbstractMethodDeclaration).generateCode(ClassScope, ClassFile) line: 281	
>TypeDeclaration.generateCode(ClassFile) line: 583	
>TypeDeclaration.generateCode(CompilationUnitScope) line: 653	
>CompilationUnitDeclaration.generateCode() line: 410	
>
>	length = this.numberOfStackItems;
>	if (length != 0) {
>the length is -1 is here
>
>and an allocation of an array of negative size, causes NegativeArraySizeException which causes the abort
>106: iload_3
>107: tableswitch
>125: iload_3
>126: tableswitch
>145: iconst_0
>146: goto
>149: new
>152: dup
>153: invokespecial
>156: throw => At this point, the error occurs
>
>Javac13 generated code â [disassembled by javap13 -p -c -v]
>  public static int foo(int) throws java.lang.Exception;
>    descriptor: (I)I
>    flags: (0x0009) ACC_PUBLIC, ACC_STATIC
>    Code:
>      stack=2, locals=2, args_size=1
>         0: iload_0
>         1: lookupswitch  { // 1
>                       0: 20
>                 default: 52
>            }
>        20: iload_0
>        21: lookupswitch  { // 1
>                       0: 40
>                 default: 44
>            }
>        40: iconst_0
>        41: goto          53
>        44: new           #7                  // class java/lang/Exception
>        47: dup
>        48: invokespecial #9                  // Method java/lang/Exception."<init>":()V
>        51: athrow
>        52: iconst_0
>        53: istore_1
>        54: iload_1
>        55: ireturn
>      LineNumberTable:
>        line 4: 0
>        line 5: 20
>        line 6: 40
>        line 7: 44
>        line 9: 52
>        line 11: 54
>      StackMapTable: number_of_entries = 5
>        frame_type = 20 /* same */
>        frame_type = 19 /* same */
>        frame_type = 3 /* same */
>        frame_type = 7 /* same */
>        frame_type = 64 /* same_locals_1_stack_item */
>          stack = [ int ]
>    Exceptions:
>      throws java.lang.Exception
>

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