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Declaring a 0-sized array (e.g 'char arr[0];') as the last member of a
structure is a GNU extension that was used to implement flexible array
members (FAMs) before they were standardised in C99 as simply '[]'.
The GNU extension itself was introduced to work around a hack of
declaring 1-sized arrays to mean a variable-length object. The advantage
of the 0-sized (and true FAMs) is that they don't count towards the size
of the structure.
Unit already declares some true FAMs, but it also declared some 0-sized
arrays.
Converting these 0-sized arrays to true FAMs is not only good for
consistency but will also allow better compiler checks now (as in a C99
FAM *must* be the last member of a structure and the compiler will warn
otherwise) and in the future as doing this fixes a bunch of warnings
(treated as errors in Unit by default) when compiled with
-O2 -Warray-bounds -Wstrict-flex-arrays -fstrict-flex-arrays=3
(Note -Warray-bounds is enabled by -Wall and -Wstrict-flex-arrays seems
to also be enabled via -Wall -Wextra, the -02 is required to make
-fstrict-flex-arrays more effective, =3 is the default on at least GCC
14)
such as
CC build/src/nxt_upstream.o
src/nxt_upstream.c: In function ‘nxt_upstreams_create’:
src/nxt_upstream.c:56:18: error: array subscript i is outside array bounds of ‘nxt_upstream_t[0]’ {aka ‘struct nxt_upstream_s[]’} [-Werror=array-bounds=]
56 | string = nxt_str_dup(mp, &upstreams->upstream[i].name, &name);
| ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
In file included from src/nxt_upstream.c:9:
src/nxt_upstream.h:55:48: note: while referencing ‘upstream’
55 | nxt_upstream_t upstream[0];
| ^~~~~~~~
Making our flexible array members proper C99 FAMs and ensuring any >0
sized trailing arrays in structures are really normal arrays will allow
to enable various compiler options (such as the above and more) that
will help keep our array usage safe.
Changing 0-sized arrays to FAMs should have no effect on structure
layouts/sizes (they both have a size of 0, although doing a sizeof() on
a FAM will result in a compiler error).
Looking at pahole(1) output for the nxt_http_route_ruleset_t structure
for the [0] and [] cases...
$ pahole -C nxt_http_route_ruleset_t /tmp/build/src/nxt_http_route.o
typedef struct {
uint32_t items; /* 0 4 */
/* XXX 4 bytes hole, try to pack */
nxt_http_route_rule_t * rule[]; /* 8 0 */
/* size: 8, cachelines: 1, members: 2 */
/* sum members: 4, holes: 1, sum holes: 4 */
/* last cacheline: 8 bytes */
} nxt_http_route_ruleset_t;
$ pahole -C nxt_http_route_ruleset_t build/src/nxt_http_route.o
typedef struct {
uint32_t items; /* 0 4 */
/* XXX 4 bytes hole, try to pack */
nxt_http_route_rule_t * rule[]; /* 8 0 */
/* size: 8, cachelines: 1, members: 2 */
/* sum members: 4, holes: 1, sum holes: 4 */
/* last cacheline: 8 bytes */
} nxt_http_route_ruleset_t;
Also checking with the size(1) command on the effected object files
shows no changes to their sizes
$ for file in build/src/nxt_upstream.o \
build/src/nxt_upstream_round_robin.o \
build/src/nxt_h1proto.o \
build/src/nxt_http_route.o \
build/src/nxt_http_proxy.o \
build/src/python/*.o; do \
size -G /tmp/${file} $file; echo; done
text data bss total filename
640 418 0 1058 /tmp/build/src/nxt_upstream.o
640 418 0 1058 build/src/nxt_upstream.o
text data bss total filename
929 351 0 1280 /tmp/build/src/nxt_upstream_round_robin.o
929 351 0 1280 build/src/nxt_upstream_round_robin.o
text data bss total filename
11707 8281 16 20004 /tmp/build/src/nxt_h1proto.o
11707 8281 16 20004 build/src/nxt_h1proto.o
text data bss total filename
8319 3101 0 11420 /tmp/build/src/nxt_http_route.o
8319 3101 0 11420 build/src/nxt_http_route.o
text data bss total filename
1495 1056 0 2551 /tmp/build/src/nxt_http_proxy.o
1495 1056 0 2551 build/src/nxt_http_proxy.o
text data bss total filename
4321 2895 0 7216 /tmp/build/src/python/nxt_python_asgi_http-python.o
4321 2895 0 7216 build/src/python/nxt_python_asgi_http-python.o
text data bss total filename
4231 2266 0 6497 /tmp/build/src/python/nxt_python_asgi_lifespan-python.o
4231 2266 0 6497 build/src/python/nxt_python_asgi_lifespan-python.o
text data bss total filename
12051 6090 8 18149 /tmp/build/src/python/nxt_python_asgi-python.o
12051 6090 8 18149 build/src/python/nxt_python_asgi-python.o
text data bss total filename
28 1963 432 2423 /tmp/build/src/python/nxt_python_asgi_str-python.o
28 1963 432 2423 build/src/python/nxt_python_asgi_str-python.o
text data bss total filename
5818 3518 0 9336 /tmp/build/src/python/nxt_python_asgi_websocket-python.o
5818 3518 0 9336 build/src/python/nxt_python_asgi_websocket-python.o
text data bss total filename
4391 2089 168 6648 /tmp/build/src/python/nxt_python-python.o
4391 2089 168 6648 build/src/python/nxt_python-python.o
text data bss total filename
9095 5909 152 15156 /tmp/build/src/python/nxt_python_wsgi-python.o
9095 5909 152 15156 build/src/python/nxt_python_wsgi-python.o
Link: <https://lwn.net/Articles/908817/>
Link: <https://people.kernel.org/kees/bounded-flexible-arrays-in-c>
Signed-off-by: Andrew Clayton <a.clayton@nginx.com>
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This patch gives users the option to set a `"prefix"` attribute
for Python applications, either at the top level or for specific
`"target"`s. If the attribute is present, the value of `"prefix"`
must be a string beginning with `"/"`. If the value of the `"prefix"`
attribute is longer than 1 character and ends in `"/"`, the
trailing `"/"` is stripped.
The purpose of the `"prefix"` attribute is to set the `SCRIPT_NAME`
context value for WSGI applications and the `root_path` context
value for ASGI applications, allowing applications to properly route
requests regardless of the path that the server uses to expose the
application.
The context value is only set if the request's URL path begins with
the value of the `"prefix"` attribute. In all other cases, the
`SCRIPT_NAME` or `root_path` values are not set. In addition, for
WSGI applications, the value of `"prefix"` will be stripped from
the beginning of the request's URL path before it is sent to the
application.
Reviewed-by: Andrei Zeliankou <zelenkov@nginx.com>
Reviewed-by: Artem Konev <artem.konev@nginx.com>
Signed-off-by: Alejandro Colomar <alx@nginx.com>
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Introducting application graceful stop. For now only used when application
process reach request limit value.
This closes #585 issue on GitHub.
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Unit's ASGI implementation creates a new event loop to run an application for
each thread since 542b5b8c0647. This may cause unexpected exceptions or
strange bugs if asyncio synchronisation primitives are initialised before the
application starts (e.g. globally).
Although the approach with a new event loop for the main thread is consistent
and helps to prepare the application to run in multiple threads, it can be a
source of pain for people who just want to run single-threaded ASGI
applications in Unit.
This is related to #560 issue on GitHub.
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This closes #459 issue on GitHub.
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PyUnicode_GET_SIZE() in deprecated since 3.3 and will be removed in 3.12.
In version 3.9 it was explicitly marked by deprecation warning causing
compilation error with Unit.
PyUnicode_GET_LENGTH() must be used instead.
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This closes #461 issue on GitHub.
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This is required for futher ASGI implementation.
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