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nxt_min()
nxt_max()
Return the minimum/maximum of two values.
nxt_swap()
Swap the values of two variables passed by their addresses.
nxt_sizeof_array()
Return the size (in bytes) of an array.
nxt_nitems()
Return the number of elements in an array.
nxt_memberof()
Expand to a member of a structure. It uses a compound literal for
the object.
nxt_sizeof_incomplete()
Calculate the size of an incomplete type, as if sizeof() could be
applied to it.
nxt_sizeof_fam0()
Calculate the size of each element of a FAM of a structure.
nxt_sizeof_fam()
Calculate the size of a FAM of a structure.
nxt_offsetof_fam()
Calculate the offset of the nth element of the FAM from the start of
the containing structure.
nxt_sizeof_struct()
Calculate the total size of a structure containing a FAM. This
value is the one that should be used for allocating the structure.
Suggested-by: Andrew Clayton <a.clayton@nginx.com>
nxt_is_near_end()
Evaluate to true if the member is near the end of a structure. This
is only designed to be used with FAMs, to make sure that the FAM is
near the end of the structure (a zero-length array near the end of
the structure would still pass this test, but it's a reasonable
assertion to do.
Suggested-by: David Laight <David.Laight@ACULAB.COM>
nxt_is_zero_sizeof()
Evaluate to true if the size of 'x' is 0.
nxt_is_same_type()
Evaluate to true if the both arguments are compatible types.
nxt_is_same_typeof()
Evaluate to true if the types of both arguments are compatible.
nxt_is_array()
Evaluate to true if the argument is an array.
nxt_must_be()
It's like static_assert(3), but implemented as an expression. It's
necessary for writing the must_be_array() macro. It's always
evaluates to (int) 0.
nxt_must_be_array()
Statically assert that the argument is an array. It is an
expression that always evaluates to (int) 0.
nxt_must_be_zero_sizeof()
Statically assert that the argument has a size of 0.
nxt_must_be_near_end()
Statically assert that a member of a structure is near the end of
it.
Suggested-by: David Laight <David.Laight@ACULAB.COM>
nxt_must_be_fam()
Statically assert that the argument is a flexible array member
(FAM). It's an expression that always evaluates to (int) 0.
Link: <https://gustedt.wordpress.com/2011/03/14/flexible-array-member/>
Link: <https://lore.kernel.org/lkml/202308161913.91369D4A@keescook/T/>
Link: <https://inbox.sourceware.org/gcc/dac8afb7-5026-c702-85d2-c3ad977d9a48@kernel.org/T/>
Link: <https://stackoverflow.com/a/57537491>
Link: <https://github.com/shadow-maint/shadow/pull/762>
Cc: Andrew Clayton <a.clayton@nginx.com>
Cc: Zhidao Hong <z.hong@f5.com>
Signed-off-by: Alejandro Colomar <alx@nginx.com>
Signed-off-by: Alejandro Colomar <alx@kernel.org>
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We had a mix of styles for declaring function-like macros:
Style A:
#define \
foo() \
do { \
... \
} while (0)
Style B:
#define foo() \
do { \
... \
} while (0)
We had a similar number of occurences of each style:
$ grep -rnI '^\w*(.*\\' | wc -l
244
$ grep -rn 'define.*(.*)' | wc -l
239
(Those regexes aren't perfect, but a very decent approximation.)
Real examples:
$ find src -type f | xargs sed -n '/^nxt_double_is_zero/,/^$/p'
nxt_double_is_zero(f) \
(fabs(f) <= FLT_EPSILON)
$ find src -type f | xargs sed -n '/define nxt_http_field_set/,/^$/p'
#define nxt_http_field_set(_field, _name, _value) \
do { \
(_field)->name_length = nxt_length(_name); \
(_field)->value_length = nxt_length(_value); \
(_field)->name = (u_char *) _name; \
(_field)->value = (u_char *) _value; \
} while (0)
I'd like to standardize on a single style for them, and IMO,
having the identifier in the same line as #define is a better
option for the following reasons:
- Programmers are used to `#define foo() ...` (readability).
- One less line of code.
- The program for finding them is really simple (see below).
function grep_ngx_func()
{
if (($# != 1)); then
>&2 echo "Usage: ${FUNCNAME[0]} <func>";
return 1;
fi;
find src -type f \
| grep '\.[ch]$' \
| xargs grep -l "$1" \
| sort \
| xargs pcregrep -Mn "(?s)^\$[\w\s*]+?^$1\(.*?^}";
find src -type f \
| grep '\.[ch]$' \
| xargs grep -l "$1" \
| sort \
| xargs pcregrep -Mn "(?s)define $1\(.*?^$" \
| sed -E '1s/^[^:]+:[0-9]+:/&\n\n/';
}
$ grep_ngx_func
Usage: grep_ngx_func <func>
$ grep_ngx_func nxt_http_field_set
src/nxt_http.h:98:
#define nxt_http_field_set(_field, _name, _value) \
do { \
(_field)->name_length = nxt_length(_name); \
(_field)->value_length = nxt_length(_value); \
(_field)->name = (u_char *) _name; \
(_field)->value = (u_char *) _value; \
} while (0)
$ grep_ngx_func nxt_sprintf
src/nxt_sprintf.c:56:
u_char * nxt_cdecl
nxt_sprintf(u_char *buf, u_char *end, const char *fmt, ...)
{
u_char *p;
va_list args;
va_start(args, fmt);
p = nxt_vsprintf(buf, end, fmt, args);
va_end(args);
return p;
}
................
Scripted change:
................
$ find src -type f \
| grep '\.[ch]$' \
| xargs sed -i '/define *\\$/{N;s/ *\\\n/ /;s/ //}'
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When testing some configurations of compilers and OSes, I noticed
that clang(1) 13 on Debian caused a function to be compiled but
unused, and the compiler triggered a compile error.
To avoid that error, use __attribute__((__unused__)). Let's call
our wrapper NXT_MAYBE_UNUSED, since it describes itself more
precisely than the GCC attribute name. It's also the name that
C2x (likely C23) has given to the standard attribute, which is
[[maybe_unused]], so it's also likely to be more readable because
of that name being in ISO C.
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This method requires as many iterations as there are set bits,
while the previous one has to shift up to the position of the
highest bit.
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