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/*-------------------------------------------------------------------------
*
* thread.c
*
* Prototypes and macros around system calls, used to help make
* threaded libraries reentrant and safe to use from threaded applications.
*
* Portions Copyright (c) 1996-2016, PostgreSQL Global Development Group
*
* src/port/thread.c
*
*-------------------------------------------------------------------------
*/
#include "c.h"
#include <pwd.h>
/*
* Threading sometimes requires specially-named versions of functions
* that return data in static buffers, like strerror_r() instead of
* strerror(). Other operating systems use pthread_setspecific()
* and pthread_getspecific() internally to allow standard library
* functions to return static data to threaded applications. And some
* operating systems have neither.
*
* Additional confusion exists because many operating systems that
* use pthread_setspecific/pthread_getspecific() also have *_r versions
* of standard library functions for compatibility with operating systems
* that require them. However, internally, these *_r functions merely
* call the thread-safe standard library functions.
*
* For example, BSD/OS 4.3 uses Bind 8.2.3 for getpwuid(). Internally,
* getpwuid() calls pthread_setspecific/pthread_getspecific() to return
* static data to the caller in a thread-safe manner. However, BSD/OS
* also has getpwuid_r(), which merely calls getpwuid() and shifts
* around the arguments to match the getpwuid_r() function declaration.
* Therefore, while BSD/OS has getpwuid_r(), it isn't required. It also
* doesn't have strerror_r(), so we can't fall back to only using *_r
* functions for threaded programs.
*
* The current setup is to try threading in this order:
*
* use *_r function names if they exit
* (*_THREADSAFE=yes)
* use non-*_r functions if they are thread-safe
*
* One thread-safe solution for gethostbyname() might be to use getaddrinfo().
*
* Run src/test/thread to test if your operating system has thread-safe
* non-*_r functions.
*/
/*
* Wrapper around strerror and strerror_r to use the former if it is
* available and also return a more useful value (the error string).
*/
char *
pqStrerror(int errnum, char *strerrbuf, size_t buflen)
{
#if defined(FRONTEND) && defined(ENABLE_THREAD_SAFETY) && defined(HAVE_STRERROR_R)
/* reentrant strerror_r is available */
#ifdef STRERROR_R_INT
/* SUSv3 version */
if (strerror_r(errnum, strerrbuf, buflen) == 0)
return strerrbuf;
else
return "Unknown error";
#else
/* GNU libc */
return strerror_r(errnum, strerrbuf, buflen);
#endif
#else
/* no strerror_r() available, just use strerror */
strlcpy(strerrbuf, strerror(errnum), buflen);
return strerrbuf;
#endif
}
/*
* Wrapper around getpwuid() or getpwuid_r() to mimic POSIX getpwuid_r()
* behaviour, if that function is not available or required.
*
* Per POSIX, the possible cases are:
* success: returns zero, *result is non-NULL
* uid not found: returns zero, *result is NULL
* error during lookup: returns an errno code, *result is NULL
* (caller should *not* assume that the errno variable is set)
*/
#ifndef WIN32
int
pqGetpwuid(uid_t uid, struct passwd * resultbuf, char *buffer,
size_t buflen, struct passwd ** result)
{
#if defined(FRONTEND) && defined(ENABLE_THREAD_SAFETY) && defined(HAVE_GETPWUID_R)
return getpwuid_r(uid, resultbuf, buffer, buflen, result);
#else
/* no getpwuid_r() available, just use getpwuid() */
errno = 0;
*result = getpwuid(uid);
/* paranoia: ensure we return zero on success */
return (*result == NULL) ? errno : 0;
#endif
}
#endif
/*
* Wrapper around gethostbyname() or gethostbyname_r() to mimic
* POSIX gethostbyname_r() behaviour, if it is not available or required.
* This function is called _only_ by our getaddinfo() portability function.
*/
#ifndef HAVE_GETADDRINFO
int
pqGethostbyname(const char *name,
struct hostent * resultbuf,
char *buffer, size_t buflen,
struct hostent ** result,
int *herrno)
{
#if defined(FRONTEND) && defined(ENABLE_THREAD_SAFETY) && defined(HAVE_GETHOSTBYNAME_R)
/*
* broken (well early POSIX draft) gethostbyname_r() which returns 'struct
* hostent *'
*/
*result = gethostbyname_r(name, resultbuf, buffer, buflen, herrno);
return (*result == NULL) ? -1 : 0;
#else
/* no gethostbyname_r(), just use gethostbyname() */
*result = gethostbyname(name);
if (*result != NULL)
*herrno = h_errno;
if (*result != NULL)
return 0;
else
return -1;
#endif
}
#endif
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