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Merge pull request #7743 from jketema/doc-fixes

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CodeQL documentation fixes
This commit is contained in:
Mathias Vorreiter Pedersen
2022-01-25 16:11:08 +00:00
committed by GitHub
parent afd6f58fe8 082c712843
commit 5d0f7efe84
2 changed files with 4 additions and 4 deletions
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6
docs/codeql/codeql-language-guides/basic-query-for-cpp-code.rst
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@@ -37,7 +37,7 @@ Running the query
import cpp
from IfStmt ifstmt, Block block
from IfStmt ifstmt, BlockStmt block
where ifstmt.getThen() = block and
block.getNumStmt() = 0
select ifstmt, "This 'if' statement is redundant."
@@ -81,10 +81,10 @@ After the initial ``import`` statement, this simple query comprises three parts
+===============================================================+===================================================================================================================+========================================================================================================================+
| ``import cpp`` | Imports the standard CodeQL libraries for C/C++. | Every query begins with one or more ``import`` statements. |
+---------------------------------------------------------------+-------------------------------------------------------------------------------------------------------------------+------------------------------------------------------------------------------------------------------------------------+
| ``from IfStmt ifstmt, Block block`` | Defines the variables for the query. | We use: |
| ``from IfStmt ifstmt, BlockStmt block`` | Defines the variables for the query. | We use: |
| | Declarations are of the form: | |
| | ``<type> <variable name>`` | - an ``IfStmt`` variable for ``if`` statements |
| | | - a ``Block`` variable for the statement block |
| | | - a ``BlockStmt`` variable for the statement block |
+---------------------------------------------------------------+-------------------------------------------------------------------------------------------------------------------+------------------------------------------------------------------------------------------------------------------------+
| ``where ifstmt.getThen() = block and block.getNumStmt() = 0`` | Defines a condition on the variables. | ``ifstmt.getThen() = block`` relates the two variables. The block must be the ``then`` branch of the ``if`` statement. |
| | | |

2
docs/codeql/writing-codeql-queries/debugging-data-flow-queries-using-partial-flow.rst
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@@ -55,7 +55,7 @@ If there are still no results and performance is still useable, then it is best
Partial flow
------------
A naive next step could be to change the sink definition to ``any()``. This would mean that we would get a lot of flow to all the places that are reachable from the sources. While this approach may work in some cases, you might find that it produces so many results that it's very hard to explore the findings. It can can also dramatically affect query performance. More importantly, you might not even see all the partial flow paths. This is because the data-flow library tries very hard to prune impossible paths and, since field stores and reads must be evenly matched along a path, we will never see paths going through a store that fail to reach a corresponding read. This can make it hard to see where flow actually stops.
A naive next step could be to change the sink definition to ``any()``. This would mean that we would get a lot of flow to all the places that are reachable from the sources. While this approach may work in some cases, you might find that it produces so many results that it's very hard to explore the findings. It can also dramatically affect query performance. More importantly, you might not even see all the partial flow paths. This is because the data-flow library tries very hard to prune impossible paths and, since field stores and reads must be evenly matched along a path, we will never see paths going through a store that fail to reach a corresponding read. This can make it hard to see where flow actually stops.
To avoid these problems, a data-flow ``Configuration`` comes with a mechanism for exploring partial flow that tries to deal with these caveats. This is the ``Configuration.hasPartialFlow`` predicate: