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Manual; Attempt to clarify section about automatic preprocessor defines configuration

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Daniel Marjamäki 2021-02-06 13:35:12 +01:00
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1 changed files with 18 additions and 23 deletions
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man/manual.md
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@ -310,7 +310,7 @@ likely you don't have to configure anything extra.
If you don't use `--project` then a bit of manual preprocessor configuration might be required. However Cppcheck has
automatic configuration of defines.
## Automatic configuration of -D
## Automatic configuration of preprocessor defines
Here is a file that has 3 bugs (when x,y,z are assigned).
@ -323,35 +323,30 @@ Here is a file that has 3 bugs (when x,y,z are assigned).
z=100/0;
#endif
Before the code is preprocessed, Cppcheck will by default look at what preprocessor conditions there are and generate
a list of suitable preprocessor configurations. For the example code above, all bugs can be found if we check for
instance the configurations "" and "A;B".
#ifndef C
#error C must be defined
#endif
Cppcheck will by default not try to check configurations that contain `#error`.
Check all code:
To find all bugs the code must be preprocessed both with "-DC" and with "-DA -DB -DC".
cppcheck file.c
=> All bugs are reported
Cppcheck automatically determines what combinations of defines are necessary to analyze all the code. The example code
above will by default automatically be preprocessed and analyzed multiple times.
### Limit automatic configurations
You can manually configure what combinations are checked with `-D`, `-U`, `--max-configs` and `--force`.
To specify a preprocessor define you can use `-D`.
The flag `-D` tells Cppcheck that a name is defined.
The flag `-U` will tell Cppcheck that a name is not defined.
The flag `--force` and `--max-configs` is used to control how many combinations are checked. When `-D` is used,
Cppcheck will only check 1 configuration unless these are used.
If there is an explicit configuration on the command line then Cppcheck will only that and nothing else.
Example:
cppcheck -DA file.c
=> Only first bug is found
You can use `--force` to tell Cppcheck that you do want to check several configurations
cppcheck -DA --force file.c
=> The first 2 bugs are found (if A is defined then the last bug never happens).
To exclude a certain define you can use `-U`. It tells Cppcheck that a macro is never defined. Example usage:
cppcheck -UA file.c
=> Cppcheck will only report the last bug.
cppcheck test.c => all bugs are found
cppcheck -DA test.c => No bug is found (#error)
cppcheck -DA -DC test.c => The first bug is found
cppcheck -UA test.c => The last bug is found
cppcheck --force -DA test.c => The two first bugs are found
## Include paths