On macOS Sierra, warning: implicit declaration of function 'getentropy'

[gareth-rees]

BPO	28676
Nosy	@ronaldoussoren, @ned-deily, @gareth-rees
PRs	[Do Not Merge] Convert Misc/NEWS so that it is managed by towncrier #552
Files	getentropy.patch

^{Note: these values reflect the state of the issue at the time it was migrated and might not reflect the current state.}

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GitHub fields:

assignee = None
closed_at = <Date 2016-11-12.21:43:39.843>
created_at = <Date 2016-11-12.19:30:20.896>
labels = ['OS-mac', 'build', '3.7']
title = "On macOS Sierra, warning: implicit declaration of function 'getentropy'"
updated_at = <Date 2017-03-31.16:36:38.720>
user = 'https://github.com/gareth-rees'

bugs.python.org fields:

activity = <Date 2017-03-31.16:36:38.720>
actor = 'dstufft'
assignee = 'none'
closed = True
closed_date = <Date 2016-11-12.21:43:39.843>
closer = 'ned.deily'
components = ['Build', 'macOS']
creation = <Date 2016-11-12.19:30:20.896>
creator = 'gdr@garethrees.org'
dependencies = []
files = ['45465']
hgrepos = []
issue_num = 28676
keywords = ['patch']
message_count = 3.0
messages = ['280669', '280672', '280674']
nosy_count = 4.0
nosy_names = ['ronaldoussoren', 'ned.deily', 'python-dev', 'gdr@garethrees.org']
pr_nums = ['552']
priority = 'normal'
resolution = 'fixed'
stage = 'resolved'
status = 'closed'
superseder = None
type = 'compile error'
url = 'https://bugs.python.org/issue28676'
versions = ['Python 2.7', 'Python 3.5', 'Python 3.6', 'Python 3.7']

[gareth-rees]

On macOS Sierra (OSX 10.12.1):

    $ ./configure --with-pydebug && make
    [... lots of output omitted ...]
    gcc -c -Wno-unused-result -Wsign-compare -g -O0 -Wall -Wstrict-prototypes    -std=c99 -Wextra -Wno-unused-result -Wno-unused-parameter -Wno-missing-field-initializers   -I. -I./Include    -DPy_BUILD_CORE -o Python/random.o Python/random.c
    Python/random.c:97:19: warning: implicit declaration of function 'getentropy' is
          invalid in C99 [-Wimplicit-function-declaration]
                res = getentropy(buffer, len);
                      ^
    1 warning generated.

This is because OSX 10.12.1 has getentropy() but does not have
getrandom(). You can see this in pyconfig.h:

    /* Define to 1 if you have the `getentropy' function. */
    #define HAVE_GETENTROPY 1

/* Define to 1 if the getrandom() function is available */
/* #undef HAVE_GETRANDOM */

and this means that in Python/random.c the header <sys/random.h> is
not included:

#  ifdef HAVE_GETRANDOM
#    include <sys/random.h>
#  elif defined(HAVE_GETRANDOM_SYSCALL)
#    include <sys/syscall.h>
#  endif

It's necessary include <sys/random.h> if either HAVE_GETRANDOM or
HAVE_GETENTROPY is defined.

[python-dev]

New changeset 828251c2bccf by Ned Deily in branch '2.7':
Issue bpo-28676: Prevent missing 'getentropy' declaration warning on macOS.
https://hg.python.org/cpython/rev/828251c2bccf

New changeset 0efd48d4c47c by Ned Deily in branch '3.5':
Issue bpo-28676: Prevent missing 'getentropy' declaration warning on macOS.
https://hg.python.org/cpython/rev/0efd48d4c47c

New changeset e2faa8a22b69 by Ned Deily in branch '3.6':
Issue bpo-28676: merge from 3.5
https://hg.python.org/cpython/rev/e2faa8a22b69

New changeset b31a7efd8b31 by Ned Deily in branch 'default':
Issue bpo-28676: merge from 3.6
https://hg.python.org/cpython/rev/b31a7efd8b31

[ned-deily]

Thanks for the patch, Gareth! Pushed for release in 2.7.13, 3.5.3, 3.6.0b4, and 3.7.0.