cp2k/docs/development/error-handling.md
2026-07-02 20:29:31 +02:00

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# Error Handling
In CP2K there exist three convenient macros for error handling. They are defined in
`src/base/base_uses.f90`, and are therefore always available. However, these macros can only be used
for **short messages** (approximately less than 7 words), because of Fortran's line length
limitation.
```
CPWARN("A short warning message")
CPABORT("A short error message")
CPASSERT(2 > 1) ! For sanity checks only, not for user errors.
```
For longer messages one can use these two routines:
```
CALL cp_warn(__LOCATION__,"A long warning message "//&
"which can span multiple lines and contains "//&
"some valuable advice for the user.")
CALL cp_abort(__LOCATION__,"A long error message "//&
"with even more valuable advice.")
```
```{note}
Messages from `CPWARN` and `cp_warn` are only printed on the first MPI-rank.
Warnings issued on other ranks are ignored.
```
## Cheat Sheet
If you want to...
- print a **short warning** message, then you should use: `CPWARN("your short message")`
- print a **longer warning** message, then you should use:
```
CALL cp_warn(__LOCATION__,"your lengthy message, "//&
"which can even span multiple lines")
```
- **stop** the program with a **short** error message, then you should use:
`CPABORT("your short message")`
- **stop** the program with a **longer** error message, then you should use:
```
CALL cp_abort(__LOCATION__,"your lengthy message, "//&
"which can even span multiple lines")
```
- have a **simple assertion** without a custom error message, then you should use:
`CPASSERT(your_logical_expression)`
- have a **simple assertion** with a **short** error message, then you should use:
```
IF(.NOT.your_logical_expression) CPABORT("your short message")
```
- have a **complex assertion** with a **short** error message, then you should use:
```
IF(.NOT.your_super_complicated_logical_expression_that_takes_alot_of_space)&
CPABORT("your short message")
```
- have a **lengthy assertion** with a **longer** error message, then you should use:
```
IF(.NOT.your_super_long_logical_expression_that_takes_alot_of_space)&
CALL cp_abort(__LOCATION__,"your lengthy message"//&
"which again can even span multiple lines")
```