Intermediate representation for multiple exception handling models

• US 7,308,680 B2
• Filed: 08/15/2006
• Issued: 12/11/2007
• Est. Priority Date: 06/26/2003
• Status: Expired due to Fees

• Current Assignee: Microsoft Technology Licensing LLC (Microsoft Corporation)
• Original Assignee: Microsoft Corporation
• Inventors: Grover, Vinod K., Sastry, Akella V. S.
• Primary Examiner(s): Dam, Tuan
• Assistant Examiner(s): RUTTEN, JAMES D
• Application Number:
  US11/505,090
• Publication Number:
  US 20070006192A1
• Time in Patent Office: 483 Days
• Field of Search: 717/114, 717/147, 717/148, 714/48
• US Class Current: 717/114
• CPC Class Codes: G06F 8/20 Software design
• CPC Class Codes: G06F 8/423 Preprocessors

Abstract

As described herein, an intermediate representation of a source code file may be used to explicitly express exception handling control flow prior to generating object code for the source code. As further described herein, a single uniform set of instructions of the intermediate representation may be used for expressing multiple different exception handling mechanisms related to multiple different programming languages. The intermediate form of the exception handling instructions may be generated by translating an intermediate language representation of the source code file. Representations of the source code in multiple different intermediate languages may be translated to a single uniform set of instructions of the intermediate representation. The intermediate form of the exception handling instructions may then be used by software development tools for such tasks as code generation, code optimization, code analysis etc. Thus, the same methods for code optimizations, analysis and generation may be used for intermediate representations of multiple different languages.

Claims

1. A method implemented at least in part by a computing device of processing a source language independent intermediate representation of software comprising exception handling constructs, the method comprising:

reading the source language independent intermediate representation of software comprising exception handling constructs;

wherein the source language independent intermediate representation explicitly expresses exception handling control flow of the software, wherein the source language independent intermediate representation comprises a single set of instructions for representing a plurality of exception handling models of a plurality of source languages, and wherein the exception handling control flow is determined using the single set of instructions by using an offset containment relationship to map offsets of protected code blocks to labels of their destination and handler blocks; and

generating, in a computer-readable media having a tangible component, a computer-readable version of the software implementing the exception handling control flow based on the source language independent intermediate representation.

2. The method of claim 1, wherein the source language independent intermediate representation comprises:

a first instruction, of the single set of instructions, for expressing transfer of control to a finalization code block;

a second instruction, of the single set of instructions, for expressing acceptance of control transfer into the finalization code block; and

a third instruction, of the single set of instructions, for expressing transfer of control out of the finalization code block.

3. The method of claim 2, wherein the finalization code block comprises code related to destructor of an object.

4. The method of claim 2, wherein the finalization block comprises code related to destructor of an expression temporary object.

5. The method of claim 2, wherein destination operands of the second instruction are the same as source operands of the third instruction.

6. The method of claim 2, wherein the first instruction for expressing explicit transfer of control to the finalization code block further comprises:

a label indicative of a beginning of the finalization code block to he used for expressing transfer of control to the finalization block; and

a label indicative of a continuation for control transfer after exiting the finalization code block.

7. The method of claim 2, wherein the second instruction for expressing acceptance of control transfer into the finalization code block is preceded by a label indicative of a beginning of the finalization code block and transfer of control to the finalization block is indicated by the use of the label.

8. The method of claim 2, wherein the third instruction for expressing transfer of control out of the finalization code block comprises fields for indicating different continuations for control transfer out of the finalization code block based on whether entry into the finalization code block was explicit or due to an exception.

9. A system for implementing source language independent exception handling intermediate representations for multiple source code languages, the system comprising:

a general purpose or specialized computer apparatus implementing an intermediate language reader, for obtaining an intermediate language representation of a source code file and generating a source language independent intermediate representation of exception handling constructs of the source code based on the intermediate language representation;

wherein the source language independent intermediate representation explicitly expresses exception handling control flow of the source code, wherein the source language independent intermediate representation comprises a single set of instructions for representing a plurality of exception handling models of the multiple source code languages, and wherein the exception handling control flow is determined using the single set of instructions by using an offset containment relationship to map offsets of protected code blocks to labels of their destination and handler blocks.

10. The system of claim 9 further comprising a compiler for generating object code based on the source language independent intermediate representation.

11. The system of claim 9, wherein the source language independent intermediate representation of the exception handling constructs further comprises a first instruction, of the single set of instructions, for catching an exception and returning an exception object related to the exception and a second instruction, of the single set of instructions, for specifying a handler for the exception based on a type value of the exception object.

12. The system of claim 11, wherein the second instruction for specifying the handler comprises:

at least one Boolean source operand for indicating the type value of the exception object;

at least one source operand indicating a label preceding a code block related to the handler to which control flow will pass if the Boolean source operand is true; and

at least one source operand indicating a label preceding a code block related to a continuation to which control flow will pass if the Boolean source operand is false.

13. The system of claim 9, wherein the source language independent intermediate representation of the exception handling constructs further comprises at least one instruction, of the single set of instructions, for specifying a handler for an exception based on a type value of an exception object related to the exception, wherein a destination operand of the at least one instruction comprises a predetermined exception object, a first source operand of the at least one instruction comprises a label indicative of a code block related to the handler and a second source operand comprises a label indicative of a code block related to a continuation.

14. The system of claim 13, wherein the at least one instruction is operative for comparing the type value of the exception object to a type value of the predetermined exception object and if there is a match, passing control flow to the code block related to the handler label and if there is no match, then passing control flow to the code block related to the continuation label.

15. The system of claim 9, wherein the source language independent intermediate representation of the exception handling constructs further comprises a first instruction, of the single set of instructions, for indicating entry into a try-except region;

and a second instruction, of the single set of instructions, for selecting one of a plurality of control flow paths for exception handling based on a type value related to an exception, wherein the plurality of control flow paths available for selection includes a path related to resumption of execution of an instruction causing the exception.

16. The system of claim 15, wherein a handler for the first instruction for indicating entry into the try-except region is the same as a handler for the exception causing instruction, and wherein the second instruction for selecting the control flow path for exception handling comprises:

an operand indicative of the type value of the exception;

a label operand indicative of a handler code block;

a label operand indicative of a continuation code block; and

a label operand indicative of the exception causing instruction.

17. A computer readable storage medium having a tangible component and having stored thereon a source language independent intermediate representation of exception handling constructs of source code, the source language independent intermediate representation of exception handling constructs comprising:

a single set of instructions for representing a plurality of exception handling models of a plurality of source languages;

a first instruction, of the single set of instructions, for catching an exception and returning an exception object related to the exception; and

a second instruction, of the single set of instructions, for specifying a handler for the exception based on a type value of the exception object;

wherein the source language independent intermediate representation explicitly expresses exception handling control flow of the source code, and wherein the exception handling control flow is determined using the single set of instructions by using an offset containment relationship to map offsets of protected code blocks to labels of their destination and handler blocks.

18. The computer readable medium of claim 17, wherein the second instruction for specifying the handler comprises:

at least one Boolean source operand for indicating the type value of the exception object;

at least one source operand indicating a label preceding a code block related to the handler to which control flow will pass if the Boolean source operand is true; and

at least one source operand indicating a label preceding a code block related to a continuation to which control flow will pass if the Boolean source operand is false.

19. The computer readable medium of claim 18, wherein the code block related to the continuation is related to a filter.

20. The computer readable medium of claim 18, wherein the code block related to the continuation comprises an unwind instruction.