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Merge pull request #1859 from geoffw0/qldocpartialdef

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CPP: Document PartialDefinitions
This commit is contained in:
Jonas Jensen
2019-09-04 09:54:55 +02:00
committed by GitHub
parent 641232a9d7 84da3e3431
commit 0e54709d47
4 changed files with 41 additions and 2 deletions
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20
cpp/ql/src/semmle/code/cpp/dataflow/internal/FlowVar.qll
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@@ -84,8 +84,13 @@ cached class FlowVar extends TFlowVar {
*
* In contrast to a normal "definition", which provides a new value for
* something, a partial definition is an expression that may affect a
* value, but does not necessarily replace it entirely. For example,
* `x.y = 1;` is a partial definition of the object `x`.
* value, but does not necessarily replace it entirely. For example:
* ```
* x.y = 1; // a partial definition of the object `x`.
* x.y.z = 1; // a partial definition of the objects `x` and `x.y`.
* x.setY(1); // a partial definition of the object `x`.
* setY(&x); // a partial definition of the object `x`.
* ```
*/
private module PartialDefinitions {
private newtype TPartialDefinition =
@@ -121,8 +126,19 @@ private module PartialDefinitions {
predicate partiallyDefinesThis(ThisExpr e) { definedExpr = e }
/**
* Gets the subBasicBlock where this `PartialDefinition` is defined.
*/
ControlFlowNode getSubBasicBlockStart() { result = node }
/**
* Gets the expression that is being partially defined. For example in the
* following code:
* ```
* x.y = 1;
* ```
* The expression `x` is being partially defined.
*/
Expr getDefinedExpr() { result = definedExpr }
Location getLocation() {

16
cpp/ql/test/library-tests/dataflow/partialdefinitions/partialdefinitions.cpp Normal file
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@@ -0,0 +1,16 @@
struct MyStruct
{
int x;
struct MySubStruct {
int z;
} y;
};
void test()
{
MyStruct s;
s.x = 1;
s.y.z = 1;
}

3
cpp/ql/test/library-tests/dataflow/partialdefinitions/partialdefinitions.expected Normal file
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@@ -0,0 +1,3 @@
| partialdefinitions.cpp:14:2:14:2 | partial def of s | partialdefinitions.cpp:14:2:14:2 | s | partialdefinitions.cpp:14:2:14:8 | ... = ... |
| partialdefinitions.cpp:15:2:15:2 | partial def of s | partialdefinitions.cpp:15:2:15:2 | s | partialdefinitions.cpp:15:2:15:10 | ... = ... |
| partialdefinitions.cpp:15:4:15:4 | partial def of y | partialdefinitions.cpp:15:4:15:4 | y | partialdefinitions.cpp:15:2:15:10 | ... = ... |

4
cpp/ql/test/library-tests/dataflow/partialdefinitions/partialdefinitions.ql Normal file
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@@ -0,0 +1,4 @@
import semmle.code.cpp.dataflow.internal.FlowVar
from PartialDefinition def
select def, def.getDefinedExpr(), def.getSubBasicBlockStart()