enomem.so

berkeley db 4.6.21的源码。berkeley db是一个简单的数据库管理系统

m4_comment([$Id: enomem.so,v 1.2 2004/09/28 14:13:09 bostic Exp $])

m4_ref_title(Upgrading m4_db Applications,
    Release 4.3: ENOMEM and DbMemoryException,,
    upgrade.4.3/fileopen, upgrade.4.3/repl)

m4_p([dnl
In versions of m4_db before 4.3, the error m4_bold(ENOMEM) was used to
indicate that the buffer in a m4_ref(Dbt) configured with
m4_ref(DB_DBT_USERMEM) was too small to hold a key or data item being
retrieved.  The 4.3 release adds a new error, m4_ref(DB_BUFFER_SMALL),
that is returned in this case.])

m4_p([dnl
The reason for the change is that the use of m4_bold(ENOMEM) was
ambiguous: calls such as m4_ref(dbh_get) or m4_ref(dbc_get) could return
m4_bold(ENOMEM) either if a m4_ref(Dbt) was too small or if some resource
was exhausted.])

m4_p([dnl
The result is that starting with the 4.3 release, C applications should
always treat m4_bold(ENOMEM) as a fatal error.  Code that checked for
the m4_bold(ENOMEM) return and allocated a new buffer should be changed
to check for m4_ref(DB_BUFFER_SMALL).])

m4_p([dnl
In C++ applications configured for exceptions, a
m4_refcxx(DbMemoryException) will continue to be thrown in both cases,
and applications should check the errno in the exception to determine
which error occurred.])

m4_p([dnl
In Java applications, a m4_bold(DbMemoryException) will be thrown
when a m4_bold(Dbt) is too small to hold a return value, and an
m4_bold(OutOfMemoryError) will be thrown in all cases of resource
exhaustion.])

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