mirror of
https://github.com/ClickHouse/ClickHouse.git
synced 2024-11-18 13:42:02 +00:00
122 lines
3.6 KiB
Markdown
122 lines
3.6 KiB
Markdown
|
|
## Developer's guide for adding new CMake options
|
|
|
|
### Don't be obvious. Be informative.
|
|
|
|
Bad:
|
|
```cmake
|
|
option (ENABLE_TESTS "Enables testing" OFF)
|
|
```
|
|
|
|
This description is quite useless as is neither gives the viewer any additional information nor explains the option purpose.
|
|
|
|
Better:
|
|
|
|
```cmake
|
|
option(ENABLE_TESTS "Provide unit_test_dbms target with Google.test unit tests" OFF)
|
|
```
|
|
|
|
If the option's purpose can't be guessed by its name, or the purpose guess may be misleading, or option has some
|
|
pre-conditions, leave a comment above the `option()` line and explain what it does.
|
|
The best way would be linking the docs page (if it exists).
|
|
The comment is parsed into a separate column (see below).
|
|
|
|
Even better:
|
|
|
|
```cmake
|
|
# implies ${TESTS_ARE_ENABLED}
|
|
# see tests/CMakeLists.txt for implementation detail.
|
|
option(ENABLE_TESTS "Provide unit_test_dbms target with Google.test unit tests" OFF)
|
|
```
|
|
|
|
### If the option's state could produce unwanted (or unusual) result, explicitly warn the user.
|
|
|
|
Suppose you have an option that may strip debug symbols from the ClickHouse's part.
|
|
This can speed up the linking process, but produces a binary that cannot be debugged.
|
|
In that case, prefer explicitly raising a warning telling the developer that he may be doing something wrong.
|
|
Also, such options should be disabled if applies.
|
|
|
|
Bad:
|
|
```cmake
|
|
option(STRIP_DEBUG_SYMBOLS_FUNCTIONS
|
|
"Do not generate debugger info for ClickHouse functions.
|
|
${STRIP_DSF_DEFAULT})
|
|
|
|
if (STRIP_DEBUG_SYMBOLS_FUNCTIONS)
|
|
target_compile_options(clickhouse_functions PRIVATE "-g0")
|
|
endif()
|
|
|
|
```
|
|
Better:
|
|
|
|
```cmake
|
|
# Provides faster linking and lower binary size.
|
|
# Tradeoff is the inability to debug some source files with e.g. gdb
|
|
# (empty stack frames and no local variables)."
|
|
option(STRIP_DEBUG_SYMBOLS_FUNCTIONS
|
|
"Do not generate debugger info for ClickHouse functions."
|
|
${STRIP_DSF_DEFAULT})
|
|
|
|
if (STRIP_DEBUG_SYMBOLS_FUNCTIONS)
|
|
message(WARNING "Not generating debugger info for ClickHouse functions")
|
|
target_compile_options(clickhouse_functions PRIVATE "-g0")
|
|
endif()
|
|
```
|
|
|
|
### In the option's description, explain WHAT the option does rather than WHY it does something.
|
|
|
|
The WHY explanation should be placed in the comment.
|
|
You may find that the option's name is self-descriptive.
|
|
|
|
Bad:
|
|
|
|
```cmake
|
|
option(ENABLE_THINLTO "Enable Thin LTO. Only applicable for clang. It's also suppressed when building with tests or sanitizers." ON)
|
|
```
|
|
|
|
Better:
|
|
|
|
```cmake
|
|
# Only applicable for clang.
|
|
# Turned off when building with tests or sanitizers.
|
|
option(ENABLE_THINLTO "Clang-specific link time optimisation" ON).
|
|
```
|
|
|
|
### Don't assume other developers know as much as you do.
|
|
|
|
In ClickHouse, there are many tools used that an ordinary developer may not know. If you are in doubt, give a link to
|
|
the tool's docs. It won't take much of your time.
|
|
|
|
Bad:
|
|
|
|
```cmake
|
|
option(ENABLE_THINLTO "Enable Thin LTO. Only applicable for clang. It's also suppressed when building with tests or sanitizers." ON)
|
|
```
|
|
|
|
Better (combined with the above hint):
|
|
|
|
```cmake
|
|
# https://clang.llvm.org/docs/ThinLTO.html
|
|
# Only applicable for clang.
|
|
# Turned off when building with tests or sanitizers.
|
|
option(ENABLE_THINLTO "Clang-specific link time optimisation" ON).
|
|
```
|
|
|
|
Other example, bad:
|
|
|
|
```cmake
|
|
option (USE_INCLUDE_WHAT_YOU_USE "Use 'include-what-you-use' tool" OFF)
|
|
```
|
|
|
|
Better:
|
|
|
|
```cmake
|
|
# https://github.com/include-what-you-use/include-what-you-use
|
|
option (USE_INCLUDE_WHAT_YOU_USE "Reduce unneeded #include s (external tool)" OFF)
|
|
```
|
|
|
|
### Prefer consistent default values.
|
|
|
|
CMake allows you to pass a plethora of values representing boolean `true/false`, e.g. `1, ON, YES, ...`.
|
|
Prefer the `ON/OFF` values, if possible.
|