US5615369A
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US
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Automated detection and correction of uninitialized variables
Assignee: Hewlett Packard Development Co LP
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Filing: 1994-07-25
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Granted: 1997-03-25
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Expires: 2014-07-25
Abstract
Abstract In a compiler within a computing system, user definition webs are built for local variables in a subroutine. For each user definition web in which a first local variable is used, if there is a use of the first local variable for which there is no definition on at least one path to an entry point of the subroutine, a definition of the local variable is inserted at every entry point of the subroutine from which the use can be reached. Further, in the preferred embodiment, for each user definition web in which a first local variable is used, if there is a use of the first local variable for which there is no definition on at least one path to an entry point of the subroutine and if no definition can reach the use, the web is reported as definitely undefined. For each user definition web in which a first local variable is used, if there is a use of the first local variable for which there is no definition and if a definition can reach the use, the web is reported as possibly undefined.
Inventors
- 👤 Anne M. Holler
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-04 02:56
CPC Classifications
G; G06; G06F; G06F8/00; G06F8/40; G06F8/41; G06F8/42; G06F8/425
Claims Analysis
Total Claims: 16
Claim 1
Independent Claim
130 words
In a compiler within a computing system, a computer implemented method comprising the steps of: (a) for local variables in a subroutine, building user definition webs, a first user definition web for a first variable including every instruction within the subroutine which defines or uses the first variable; and, (b) for the first user definition web when the first local variable is used at least once, performing the following substep: (b.1) if there is a use of the first local variable for which there is no definition on a path to an entry point of the subroutine, performing the following substeps: (b.1.1) if no definition can reach the use, report the web as definitely undefined, and (b.1.2) if a definition can reach the use, report the web as possibly undefined.
Claim 2
Dependent Claim
130 words
In a compiler within a computing system, a computer implemented method comprising the steps of: (a) for local variables in a subroutine, building user definition webs, a first user definition web for a first variable including every instruction within the subroutine which defines or uses the first variable; and, (b) for the first user definition web when the first local variable is used at least once, performing the following substep: (b.1) if there is a use of the first local variable for which there is no definition on a path to an entry point of the subroutine, performing the following substeps: (b.1.1) if no definition can reach the use, report the web as definitely undefined, and (b.1.2) if a definition can reach the use, report the web as possibly undefined.
Claim 3
Dependent Claim
59 words
A method as in claim 1 wherein substep (b.1.1) includes, if no definition can reach the use, inserting a definition of the first local variable at every entry point of the subroutine; and wherein substep (b.1.2) includes, if a definition can reach the use, inserting a definition of the first local variable at every entry point of the subroutine.
Claim 4
Dependent Claim
73 words
A method as in claim 1 wherein substep (b.1.1) includes, if no definition can reach the use, inserting a definition of the first local variable at every entry point of the subroutine from which the use can be reached; and wherein substep (b.1.2) includes, if a definition can reach the use, inserting a definition of the first local variable at every entry point of the subroutine from which the use can be reached.
Claim 5
Dependent Claim
124 words
In a compiler within a computing system, a computer implemented method comprising the steps of: (a) for local variables in a subroutine, building user definition webs, a first user definition web for a first variable including every instruction within the subroutine which defines or uses the first variable; and, (b) for the first user definition web when the first local variable is used at least once, performing the following substep: (b.1) if there is a use of the first local variable for which there is no definition on a path to an entry point of the subroutine, performing the following substep: (b.1.1) inserting a definition of the first local variable at every entry point of the subroutine from which the use can be reached.
Claim 6
Dependent Claim
124 words
In a compiler within a computing system, a computer implemented method comprising the steps of: (a) for local variables in a subroutine, building user definition webs, a first user definition web for a first variable including every instruction within the subroutine which defines or uses the first variable; and, (b) for the first user definition web when the first local variable is used at least once, performing the following substep: (b.1) if there is a use of the first local variable for which there is no definition on a path to an entry point of the subroutine, performing the following substep: (b.1.1) inserting a definition of the first local variable at every entry point of the subroutine from which the use can be reached.
Claim 7
Dependent Claim
88 words
A method as in claim 4, wherein step (b) additionally comprises the following substep, performed for each user definition web in which the first local variable is used: (b.2) if there is a use of the first local variable for which there is no definition on a path to an entry point of the subroutine, performing the following substeps: (b.2.1) if no definition can reach the use, report the web as definitely undefined, and (b.2.2) if a definition can reach the use, report the web as possibly undefined.
Claim 8
Dependent Claim
25 words
A method as in claim 4 wherein substep (b.1.1) includes inserting a definition of the first local variable at every entry point of the subroutine.
Claim 9
Dependent Claim
139 words
Storage media which contains software which, when run on an appropriate computing system, performs a method within a compiler which comprises the steps of: (a) for local variables in a subroutine, building user definition webs, a first user definition web for a first variable including every instruction within the subroutine which defines or uses the first variable; and, (b) for the first user definition web when the first local variable is used at least once, performing the following substep: (b.1) if there is a use of the first local variable for which there is no definition on a path to an entry point of the subroutine, performing the following substeps: (b.1.1) if no definition can reach the use, report the web as definitely undefined, and (b.1.2) if a definition can reach the use, report the web as possibly undefined.
Claim 10
Dependent Claim
139 words
Storage media which contains software which, when run on an appropriate computing system, performs a method within a compiler which comprises the steps of: (a) for local variables in a subroutine, building user definition webs, a first user definition web for a first variable including every instruction within the subroutine which defines or uses the first variable; and, (b) for the first user definition web when the first local variable is used at least once, performing the following substep: (b.1) if there is a use of the first local variable for which there is no definition on a path to an entry point of the subroutine, performing the following substeps: (b.1.1) if no definition can reach the use, report the web as definitely undefined, and (b.1.2) if a definition can reach the use, report the web as possibly undefined.
Claim 11
Dependent Claim
59 words
Storage media as in claim 7 wherein substep (b.1.1) includes, if no definition can reach the use, inserting a definition of the first local variable at every entry point of the subroutine; and wherein substep (b.1.2) includes, if a definition can reach the use, inserting a definition of the first local variable at every entry point of the subroutine.
Claim 12
Dependent Claim
73 words
Storage media as in claim 7 wherein substep (b.1.1) includes, if no definition can reach the use, inserting a definition of the first local variable at every entry point of the subroutine from which the use can be reached; and wherein substep (b.1.2) includes, if a definition can reach the use, inserting a definition of the first local variable at every entry point of the subroutine from which the use can be reached.
Claim 13
Dependent Claim
133 words
Storage media which contains software which, when run on an appropriate computing system, performs a method within a compiler which comprises the steps of: (a) for local variables in a subroutine, building user definition webs, a first user definition web for a first variable including every instruction within the subroutine which defines or uses the first variable; and, (b) for the first user definition web when the first local variable is used at least once, performing the following substep: (b.1) if there is a use of the first local variable for which there is no definition on a path to an entry point of the subroutine, performing the following substep: (b.1.1) inserting a definition of the first local variable at every entry point of the subroutine from which the use can be reached.
Claim 14
Dependent Claim
133 words
Storage media which contains software which, when run on an appropriate computing system, performs a method within a compiler which comprises the steps of: (a) for local variables in a subroutine, building user definition webs, a first user definition web for a first variable including every instruction within the subroutine which defines or uses the first variable; and, (b) for the first user definition web when the first local variable is used at least once, performing the following substep: (b.1) if there is a use of the first local variable for which there is no definition on a path to an entry point of the subroutine, performing the following substep: (b.1.1) inserting a definition of the first local variable at every entry point of the subroutine from which the use can be reached.
Claim 15
Dependent Claim
88 words
Storage media as in claim 10, wherein step (b) additionally comprises the following substep, performed for each user definition web in which the first local variable is used: (b.2) if there is a use of the first local variable for which there is no definition on a path to an entry point of the subroutine, performing the following substeps: (b.2.1) if no definition can reach the use, report the web as definitely undefined, and (b.2.2) if a definition can reach the use, report the web as possibly undefined.
Claim 16
Dependent Claim
25 words
Storage media as in claim 10 wherein substep (b.1.1) includes inserting a definition of the first local variable at every entry point of the subroutine.
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 2000-03-24 | 2000-09-23 | 2001-03-25 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 2004-03-24 | 2004-09-23 | 2005-03-25 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2008-03-24 | 2008-09-23 | 2009-03-25 | $7700.00 | Window Closed / Lapsed |