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121 lines
4.4 KiB
Plaintext
121 lines
4.4 KiB
Plaintext
Refer also to this page for more information -
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https://docs.libretro.com/development/coding-standards/
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Struct ordering
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---------------
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For POD-types, try to order structs as follows (first to last):
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* long double (8 bytes, 16 bytes [64bit x86], 12 bytes [32bit x86])
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* double (8 bytes)
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* int64_t (8 bytes, 8 bytes [32bit ARM],
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4 bytes [32bit x86])
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* uint64_t (4 bytes [32bit], 8 bytes [32bit ARM], 8 bytes [64bit])
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* pointer (4 bytes [32bit], 8 bytes [64bit] [1])
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* intptr_t (4 bytes [32bit], 8 bytes [64bit] [1])
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* uintptr_t (4 bytes [32bit], 8 bytes [64bit] [1])
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* ptrdiff_t (4 bytes [32bit], 8 bytes [64bit] [1])
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* ssize_t (4 bytes [32bit], 8 bytes [64bit])
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* size_t (4 bytes [32bit], 8 bytes [64bit])
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* jmp_buf (4 bytes)
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* long (4 bytes [64bit Win], 8 bytes [64bit non-Win],
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4 bytes [32bit])
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* int32_t (4 bytes)
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* unsigned (4 bytes)
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* float (4 bytes)
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* int (4 bytes)
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* enum (4 bytes)
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* int16_t (2 bytes)
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* char (1 byte)
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* bool (1 byte)
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[1] PS3 uses 4 byte pointers despite having a 64bit processor
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Struct members should be sorted by alignment. Therefore, structs
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should be sorted by the largest type inside them.
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For example, take a struct like this:
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typedef struct
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{
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size_t capacity;
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bool old_format;
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bool compress;
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bool fuzzy_archive_match;
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bool autofix_paths;
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char path[PATH_MAX_LENGTH];
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char base_content_directory[PATH_MAX_LENGTH];
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} playlist_config_t;
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size_t has the biggest alignment here, so 'struct playlist_config_t'
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inside a struct should come before or after size_t.
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*** BEST PRACTICES ***
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* If we have pointers and size variable pairs, it's best to
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interleave them to increase the probability they go in the
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same cacheline. It also makes the code more readable, that
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these two variables are connected.
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Example:
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struct a
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{
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char* b;
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size_t b_len;
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char* c;
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size_t c_len;
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};
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Stack size
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----------
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You have to assume that stack size is going to be limited in
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RetroArch. Some game consoles (and other embedded systems)
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might have a default stack size as low as 128Kb or less.
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Be conservative with stack size but don't try to put very
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small structs on heap either [to avoid memory fragmentation
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among other things]. A balancing act here is necessary.
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Be mindful that heap allocations are slow compared to stack.
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Functions
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---------
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- Avoid doing small getter/setter functions. We want a function
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to justify its function call overhead by doing a significant
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body of work. Small one-line getter/setter functions for what
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is predominantly C-style structs is not useful, plus it leads
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to people thinking this function is more complex than it
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actually is, thus obfuscating the sourcecode instead of it
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being easier to read.
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If you can find examples in the codebase that violate this
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guideline, do not hesitate to point them out to us.
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Variable declaration
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--------------------
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For C source files, we have to insist you stick to the following:
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- Declare variables either at the start of a function or the start
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of a code block, depending on the scope they need.
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- Do not do initial for loop declarations. Refer to the bulletpoint above:
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either declare them at the start of the function, or at the start
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of the code block.
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Not doing this would break compilation on platforms where we are compiling
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these C source files in C89 compatibility mode. If such issues occur in pull
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requests, we have to request that it be fixed.
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VLA (Variable Length Array)
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---------------------------
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Do not use VLAs (Variable Length Array) in C source files. These are not
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C89-compliant.
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Miscellaneous
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-------------
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- Brace usage follows "Allman style". The brace associated with a control statement is placed on the following line,
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indented to the same level as the control statement.
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Statements within the braces are indented to the next level.
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- A single statement block must not include brackets (unless the block uses a macro that expands into multiple lines)
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- If possible, avoid 'while (true)' and use 'for (;;)' instead
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