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| author | The Android Open Source Project <initial-contribution@android.com> | 2008-12-17 18:03:55 -0800 |
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| committer | The Android Open Source Project <initial-contribution@android.com> | 2008-12-17 18:03:55 -0800 |
| commit | 89c1feb0a69a7707b271086e749975b3f7acacf7 (patch) | |
| tree | 003624a03635e05020a47fc72a2c42934e3f0703 /docs/java-constraints.html | |
| parent | 2ad60cfc28e14ee8f0bb038720836a4696c478ad (diff) | |
| download | android_dalvik-89c1feb0a69a7707b271086e749975b3f7acacf7.tar.gz android_dalvik-89c1feb0a69a7707b271086e749975b3f7acacf7.tar.bz2 android_dalvik-89c1feb0a69a7707b271086e749975b3f7acacf7.zip | |
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diff --git a/docs/java-constraints.html b/docs/java-constraints.html new file mode 100644 index 000000000..2410a1e7f --- /dev/null +++ b/docs/java-constraints.html @@ -0,0 +1,1080 @@ +<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd"> + +<html> + <head> + <title>Java bytecode constraints</title> + <link rel=stylesheet href="java-constraints.css"> + </head> + + <body> + <h1> + Bytecode constraints + </h1> + + <p> + From the point of view of a piece of code written in the Java + programming language or targeted in the same way to <code>.class</code> + files, the Dalvik VM aims to behave in a way + that is fully consistent with the language's definition. + That is, the code running in Dalvik will behave the same as it + would have running in any other virtual machine. This includes + verification failures. + The Dx/Dalvik system will check roughly the same + constraints that any other VM would, except as noted in the file + <a href="verifier.html">verifier.html</a>. The following table briefly + lists all Dx/Dalvik verification constraints together their analogs + from the book <i>The Java<super>TM</super> Language Specification</i>, + second edition. In the numbering scheme, the first three + elements refer to the specification chapter, the fourth one to the + bullet inside that chapter. The failure mode specifies whether the + constraint will fail during the Dx conversion or during verification in + the VM itself. + </p> + + <h2> + Static constraints + </h2> + + <p> + Static constraints are constraints on individual elements of the bytecode. + They usually can be checked without employing control or data-flow analysis + techniques. + </p> + + <table> + <tr> + <th> + Identifier + </th> + + <th> + Description + </th> + + <th> + Spec equivalent + </th> + + <th> + Failure mode + </th> + </tr> + + <tr> + <td> + A1 + </td> + + <td> + The <code>code</code> array must not be empty. + </td> + + <td> + 4.8.1.1 + </td> + + <td> + DX + </td> + </tr> + + <tr> + <td> + A2 + </td> + + <td> + The <code>code</code> array must not be larger than 65535 bytes. + </td> + + <td> + 4.8.1.2 + </td> + + <td> + DX + </td> + </tr> + + <tr> + <td> + A3 + </td> + + <td> + The first opcode in <code>code</code> array must have index + <code>0</code>. + </td> + + <td> + 4.8.1.3 + </td> + + <td> + DX + </td> + </tr> + + <tr> + <td> + A4 + </td> + + <td> + The <code>code</code> array must only contain valid opcodes. + </td> + + <td> + 4.8.1.4 + </td> + + <td> + DX + </td> + </tr> + + <tr> + <td> + A5 + </td> + + <td> + The index of instruction <code>n+1</code> must equal the index of + instruction <code>n</code> plus the length of instruction + <code>n</code>, taking into account a possible <code>wide</code> + instruction. Opcodes modified by a <code>wide</code> instruction must + not be directly reachable. + </td> + + <td> + 4.8.1.5 + </td> + + <td> + DX + </td> + </tr> + + <tr> + <td> + A6 + </td> + + <td> + The last instruction in <code>code</code> array must end at index + <code>code_length-1</code>. + </td> + + <td> + 4.8.1.6 + </td> + + <td> + DX + </td> + </tr> + + <tr> + <td> + A7 + </td> + + <td> + All jump and branch targets must be opcodes within the same method. + Opcodes modified by a <code>wide</code> instruction must not be + directly reachable via a jump or branch instruction. + </td> + + <td> + 4.8.1.7 + </td> + + <td> + DX + </td> + </tr> + + <tr> + <td> + A8 + </td> + + <td> + All targets of a <code>tableswitch</code> instruction must be opcodes + within the same method. Upper and lower bounds must be consistent. + Opcodes modified by a <code>wide</code> instruction must not be + directly reachable via a <code>tableswitch</code> instruction. + </td> + + <td> + 4.8.1.8 + </td> + + <td> + DX + </td> + </tr> + + <tr> + <td> + A9 + </td> + + <td> + All targets of a <code>lookupswitch</code> instruction must be opcodes + within the same method. Its table must be consistent and sorted + low-to-high. Opcodes modified by a <code>wide</code> instruction must + not be directly reachable via a <code>lookupswitch</code> instruction. + </td> + + <td> + 4.8.1.9 + </td> + + <td> + DX + </td> + </tr> + + <tr> + <td> + A10 + </td> + + <td> + The operands of <code>ldc</code> and <code>ldc_w</code> instructions + must be valid indices into the constant pool. The respective entries + must be of type <code>CONSTANT_Integer</code>, + <code>CONSTANT_Float</code>, or <code>CONSTANT_String</code>. + </td> + + <td> + 4.8.1.10 + </td> + + <td> + DX + </td> + </tr> + + <tr> + <td> + A11 + </td> + + <td> + The operands of <code>ldc2_w</code> instructions must be valid indices + into the constant pool. The respective entries must be of type + <code>CONSTANT_Long</code> or <code>CONSTANT_Double</code>. The + subsequent constant pool entry must be valid and remain unused. + </td> + + <td> + 4.8.1.11 + </td> + + <td> + DX + </td> + </tr> + + <tr> + <td> + A12 + </td> + + <td> + The Operands of <code>get<kind></code> and + <code>put<kind></code> instructions must be valid indices into + constant pool. The respective entries must be of type + <code>CONSTANT_Fieldref</code>. + </td> + + <td> + 4.8.1.12 + </td> + + <td> + DX + </td> + </tr> + + <tr> + <td> + A13 + </td> + + <td> + The first two operands of <code>invokevirtual</code>, + <code>invokespecial</code>, and <code>invokestatic</code> must form a + valid 16-bit index into the constant pool. The respective entries must + be of type <code>CONSTANT_Methodref</code>. + </td> + + <td> + 4.8.1.13 + </td> + + <td> + DX + </td> + </tr> + + <tr> + <td> + A14 + </td> + + <td> + Methods whose names start with '<' must only be invoked implicitly by + the VM, not by class file code. The only exception is the instance + initializer, which may be invoked by <code>invokespecial</code>. + </td> + + <td> + 4.8.1.14 + </td> + + <td> + DX + </td> + </tr> + + <tr> + <td> + A15 + </td> + + <td> + The first two operands of <code>invokeinterface</code> must form a + valid 16-bit index into the constant pool. The entry must be of type + <code>CONSTANT_Interface_Methodref</code>. The third operand must + specify number of local variables and the fourth operand must always + be zero. + </td> + + <td> + 4.8.1.15 + </td> + + <td> + DX + </td> + </tr> + + <tr> + <td> + A16 + </td> + + <td> + The operands of <code>instanceof</code>, <code>checkcast</code>, + <code>new</code>, and <code>anewarray</code> instructions must + be a valid index into the constant pool. The first two operands of + <code>multianewarray</code> instruction must form a valid 16-bit index + into the constant pool. All respective entries must be of type + <code>CONSTANT_Class</code>. + </td> + + <td> + 4.8.1.16 + </td> + + <td> + DX + </td> + </tr> + + <tr> + <td> + A17 + </td> + + <td> + The dimensions of an array created by <code>anewarray</code> + instructions must be less than <code>256</code>. + </td> + + <td> + 4.8.1.17 + </td> + + <td> + DX + </td> + </tr> + + <tr> + <td> + A18 + </td> + + <td> + The <code>new</code> instruction must not reference array classes, + interfaces, or abstract classes. + </td> + + <td> + 4.8.1.18 + </td> + + <td> + DX + </td> + </tr> + + <tr> + <td> + A19 + </td> + + <td> + The type referenced by a <code>multinewarray</code> instruction must + have at least as many dimensions as specified in the instruction. The + dimensions operand must not be <code>0</code> + </td> + + <td> + 4.8.1.19 + </td> + + <td> + DX + </td> + </tr> + + <tr> + <td> + A20 + </td> + + <td> + The type referenced by a <code>newarray</code> instruction must be a + valid, non-reference type. + </td> + + <td> + 4.8.1.20 + </td> + + <td> + DX + </td> + </tr> + + <tr> + <td> + A21 + </td> + + <td> + The index operand of instructions explicitly referencing single-width + local variables must be non-negative and smaller than + <code>max_locals</code>. + </td> + + <td> + 4.8.1.21 + </td> + + <td> + DX + </td> + </tr> + + <tr> + <td> + A22 + </td> + + <td> + The index operand of instructions implicitly referencing single-width + local variables must be non-negative and smaller than + <code>max_locals</code>. + </td> + + <td> + 4.8.1.22 + </td> + + <td> + DX + </td> + </tr> + + <tr> + <td> + A23 + </td> + + <td> + The index operand of instructions explicitly referencing double-width + local variables must be non-negative and smaller than + <code>max_locals-1</code>. + </td> + + <td> + 4.8.1.23 + </td> + + <td> + DX + </td> + </tr> + + <tr> + <td> + A24 + </td> + + <td> + The index operand of instructions implicitly referencing double-width + local variables must be non-negative and smaller than + <code>max_locals-1</code>. + </td> + + <td> + 4.8.1.24 + </td> + + <td> + DX + </td> + </tr> + + <tr> + <td> + A25 + </td> + + <td> + The index operand of <code>wide</code> instructions explicitly + referencing single-width local variables must be non-negative and + smaller than <code>max_locals</code>. + </td> + + <td> + 4.8.1.25 + </td> + + <td> + DX + </td> + </tr> + + <tr> + <td> + A26 + </td> + + <td> + The index operand of <code>wide</code> instructions explicitly + referencing double-width local variables must be non-negative and + smaller than <code>max_locals-1</code>. + </td> + + <td> + 4.8.1.25 + </td> + + <td> + DX + </td> + </tr> + </table> + + <h2> + Structural constraints + </h2> + + <p> + Structural constraints are constraints on relationships between several + elements of the bytecode. They usually can't be checked without employing + control or data-flow analysis techniques. + </p> + + <table> + <tr> + <th> + Identifier + </th> + + <th> + Description + </th> + + <th> + Spec equivalent + </th> + + <th> + Failure mode + </th> + </tr> + + <tr> + <td> + B1 + </td> + + <td> + The number and types of arguments (operands and local variables) must + always match the instruction. + </td> + + <td> + 4.8.2.1 + </td> + + <td> + DX + </td> + </tr> + + <tr> + <td> + B2 + </td> + + <td> + The operand stack must have the same depth for all executions paths + leading to an instruction. + </td> + + <td> + 4.8.2.2 + </td> + + <td> + DX + </td> + </tr> + + <tr> + <td> + B3 + </td> + + <td> + Local variable pairs must never be broken up. + </td> + + <td> + 4.8.2.3 + </td> + + <td> + DX + </td> + </tr> + + <tr> + <td> + B4 + </td> + + <td> + A local variable (or pair) has to be assigned first before it can be + read. + </td> + + <td> + 4.8.2.4 + </td> + + <td> + DX + </td> + </tr> + + <tr> + <td> + B5 + </td> + + <td> + The operand stack must never grow beyond <code>max_stack</code>. + </td> + + <td> + 4.8.2.5 + </td> + + <td> + DX + </td> + </tr> + + <tr> + <td> + B6 + </td> + + <td> + The operand stack must never underflow. + </td> + + <td> + 4.8.2.6 + </td> + + <td> + DX + </td> + </tr> + + <tr> + <td> + B7 + </td> + + <td> + An <code>invokespecial</code> instruction must only invoke an instance + initializer or a method in the current class or one of its + superclasses. + </td> + + <td> + 4.8.2.7 + </td> + + <td> + VM + </td> + </tr> + + <tr> + <td> + B8 + </td> + + <td> + An instance initializer must only be invoked on an uninitialized + instance residing on the operand stack. + </td> + + <td> + 4.8.2.8 + </td> + + <td> + VM + </td> + </tr> + + <tr> + <td> + B9 + </td> + + <td> + Instance methods may only be invoked on and instance fields may only + be accessed on already initialized instances. + </td> + + <td> + 4.8.2.9 + </td> + + <td> + VM + </td> + </tr> + + <tr> + <td> + B10 + </td> + + <td> + The must be no backwards branches with uninitialized instances on the + operand stack or in local variables. There must be no code protected + by an exception handler that contains local variables with + uninitialized instances. + </td> + + <td> + 4.8.2.10 + </td> + + <td> + DX + </td> + </tr> + + <tr> + <td> + B11 + </td> + + <td> + An instance initializer must call another instance initializer (same + class or superclass) before any instance members can be accessed. + Exceptions are non-inherited instance fields, which can be assigned + before calling another initializer, and the <code>Object</code> class + in general. + </td> + + <td> + 4.8.2.11 + </td> + + <td> + VM + </td> + </tr> + + <tr> + <td> + B12 + </td> + + <td> + All actual method arguments must be assignment-compatible with formal + arguments. + </td> + + <td> + 4.8.2.12 + </td> + + <td> + VM + </td> + </tr> + + <tr> + <td> + B13 + </td> + + <td> + For each instance method invocation, the actual instance must be + assignment-compatible with the class or interface specified in the + instruction. + </td> + + <td> + 4.8.2.13 + </td> + + <td> + VM + </td> + </tr> + + <tr> + <td> + B14 + </td> + + <td> + A returns instruction must match its method's return type. + </td> + + <td> + 4.8.2.14 + </td> + + <td> + VM + </td> + </tr> + + <tr> + <td> + B15 + </td> + + <td> + When accessing protected members of a superclass, the actual type of + the instance being accessed must be either the current class or one + of its subclasses. + </td> + + <td> + 4.8.2.15 + </td> + + <td> + VM + </td> + </tr> + + <tr> + <td> + B16 + </td> + + <td> + The type of a value stored into a static field must be + assignment-compatible with or convertible to the field's type. + </td> + + <td> + 4.8.2.16 + </td> + + <td> + VM + </td> + </tr> + + <tr> + <td> + B17 + </td> + + <td> + The type of a value stored into a field must be assignment-compatible + with or convertible to the field's type. + </td> + + <td> + 4.8.2.17 + </td> + + <td> + VM + </td> + </tr> + + <tr> + <td> + B18 + </td> + + <td> + The type of every value stored into an array must be + assignment-compatible with the array's component type. + </td> + + <td> + 4.8.2.18 + </td> + + <td> + VM + </td> + </tr> + + <tr> + <td> + B19 + </td> + + <td> + The operand of an <code>athrow</code> instruction must be + assignment-compatible with <code>java.lang.Throwable</code>. + </td> + + <td> + 4.8.2.19 + </td> + + <td> + VM + </td> + </tr> + + <tr> + <td> + B20 + </td> + + <td> + The last reachable instruction of a method must either be a backwards + jump or branch, a return, or an <code>athrow</code> instruction. It + must not be possible to leave the <code>code</code> array at the + bottom. + </td> + + <td> + 4.8.2.20 + </td> + + <td> + VM + </td> + </tr> + + <tr> + <td> + B21 + </td> + + <td> + Local variable values must not be used as return addresses. + </td> + + <td> + 4.8.2.21 + </td> + + <td> + VM + </td> + </tr> + + <tr> + <td> + B22 + </td> + + <td> + There must be a single, uniquely determined return instruction per + subroutine call. + </td> + + <td> + 4.8.2.22 + </td> + + <td> + VM + </td> + </tr> + + <tr> + <td> + B23 + </td> + + <td> + Subroutine calls must not be directly or indirectly self-recursive. + </td> + + <td> + 4.8.2.23 + </td> + + <td> + DX + </td> + </tr> + + <tr> + <td> + B24 + </td> + + <td> + <code>ReturnAddress</code> instances must not be reused. If a + subroutine returns to a <code>ReturnAddress</code> further up the + stack than where its original call instruction is located, then all + <code>ReturnAddress</code> instances further down the stack must + never be used. + </td> + + <td> + 4.8.2.24 + </td> + + <td> + DX + </td> + </tr> + + </table> + </body> +</html> |