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58 lines
2.4 KiB
Markdown
58 lines
2.4 KiB
Markdown
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# HDF5 Library Code Conventions
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This document describes some practices that are new, or newly
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documented, starting in 2020.
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## Function / Variable Attributes
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In H5private.h, the library provides platform-independent macros
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for qualifying function and variable definitions.
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### Functions that accept `printf(3)` and `scanf(3)` format strings
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Label functions that accept a `printf(3)`-compliant format string with
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`H5_ATTR_FORMAT(printf,format_argno,variadic_argno)`, where
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the format string is the `format_argno`th argument (counting from 1)
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and the variadic arguments start with the `variadic_argno`th.
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Functions that accept a `scanf(3)`-compliant format string should
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be labeled `H5_ATTR_FORMAT(scanf,format_argno,variadic_argno)`.
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### Functions that do never return
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The definition of a function that always causes the program to abort and hang
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should be labeled `H5_ATTR_NORETURN` to help the compiler see which flows of
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control are infeasible.
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### Other attributes
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**TBD**
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### Unused variables and parameters
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Compilers will warn about unused parameters and variables—developers should pay
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attention to those warnings and make an effort to prevent them.
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Some function parameters and variables are unused in *all* configurations of
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the project. Ordinarily, such parameters and variables should be deleted.
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However, sometimes it is possible to foresee a parameter being used, or
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removing it would change an API, or a parameter has to be defined to conform a
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function to some function pointer type. In those cases, it's permissible to
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mark a symbol `H5_ATTR_UNUSED`.
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Other parameters and variables are unused in *some* configurations of the
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project, but not all. A symbol may fall into disuse in some configuration in
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the future—then the compiler should warn, and the symbol should not be
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defined—so developers should try to label a sometimes-unused symbol with an
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attribute that's specific to the configurations where the symbol is (or is not)
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expected to be used. The library provides the following attributes for that
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purpose:
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* `H5_ATTR_DEPRECATED_USED`: used only if deprecated symbols are enabled
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* `H5_ATTR_NDEBUG_UNUSED`: used only if `NDEBUG` is *not* \#defined
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* `H5_ATTR_DEBUG_API_USED`: used if the debug API is enabled
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* `H5_ATTR_PARALLEL_UNUSED`: used only if Parallel HDF5 *is not* configured
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* `H5_ATTR_PARALLEL_USED`: used only if Parallel HDF5 *is* configured
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Some attributes may be phased in or phased out in the future.
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