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Diffstat (limited to 'Documentation/CodingGuidelines')
| -rw-r--r-- | Documentation/CodingGuidelines | 75 |
1 files changed, 74 insertions, 1 deletions
diff --git a/Documentation/CodingGuidelines b/Documentation/CodingGuidelines index 1d92b2da03..2f35b6691f 100644 --- a/Documentation/CodingGuidelines +++ b/Documentation/CodingGuidelines @@ -204,6 +204,33 @@ For shell scripts specifically (not exhaustive): local variable="$value" local variable="$(command args)" + - The common construct + + VAR=VAL command args + + to temporarily set and export environment variable VAR only while + "command args" is running is handy, but this triggers an + unspecified behaviour according to POSIX when used for a command + that is not an external command (like shell functions). Indeed, + dash 0.5.10.2-6 on Ubuntu 20.04, /bin/sh on FreeBSD 13, and AT&T + ksh all make a temporary assignment without exporting the variable, + in such a case. As it does not work portably across shells, do not + use this syntax for shell functions. A common workaround is to do + an explicit export in a subshell, like so: + + (incorrect) + VAR=VAL func args + + (correct) + ( + VAR=VAL && + export VAR && + func args + ) + + but be careful that the effect "func" makes to the variables in the + current shell will be lost across the subshell boundary. + - Use octal escape sequences (e.g. "\302\242"), not hexadecimal (e.g. "\xc2\xa2") in printf format strings, since hexadecimal escape sequences are not portable. @@ -214,6 +241,16 @@ For C programs: - We use tabs to indent, and interpret tabs as taking up to 8 spaces. + - Nested C preprocessor directives are indented after the hash by one + space per nesting level. + + #if FOO + # include <foo.h> + # if BAR + # include <bar.h> + # endif + #endif + - We try to keep to at most 80 characters per line. - As a Git developer we assume you have a reasonably modern compiler @@ -234,7 +271,7 @@ For C programs: . since around 2007 with 2b6854c863a, we have been using initializer elements which are not computable at load time. E.g.: - const char *args[] = {"constant", variable, NULL}; + const char *args[] = { "constant", variable, NULL }; . since early 2012 with e1327023ea, we have been using an enum definition whose last element is followed by a comma. This, like @@ -531,6 +568,42 @@ For C programs: use your own debugger and arguments. Example: `GIT_DEBUGGER="ddd --gdb" ./bin-wrappers/git log` (See `wrap-for-bin.sh`.) + - The primary data structure that a subsystem 'S' deals with is called + `struct S`. Functions that operate on `struct S` are named + `S_<verb>()` and should generally receive a pointer to `struct S` as + first parameter. E.g. + + struct strbuf; + + void strbuf_add(struct strbuf *buf, ...); + + void strbuf_reset(struct strbuf *buf); + + is preferred over: + + struct strbuf; + + void add_string(struct strbuf *buf, ...); + + void reset_strbuf(struct strbuf *buf); + + - There are several common idiomatic names for functions performing + specific tasks on a structure `S`: + + - `S_init()` initializes a structure without allocating the + structure itself. + + - `S_release()` releases a structure's contents without freeing the + structure. + + - `S_clear()` is equivalent to `S_release()` followed by `S_init()` + such that the structure is directly usable after clearing it. When + `S_clear()` is provided, `S_init()` shall not allocate resources + that need to be released again. + + - `S_free()` releases a structure's contents and frees the + structure. + For Perl programs: - Most of the C guidelines above apply. |