The exclusion of SIGALRM dates back to Berkeley days, when Postgres used
SIGALRM in only one very short stretch of code. Nowadays, allowing it to
interrupt kernel calls doesn't seem like a very good idea, since its use
for statement_timeout means SIGALRM could occur anyplace in the code, and
there are far too many call sites where we aren't prepared to deal with
EINTR failures. When third-party code is taken into consideration, it
seems impossible that we ever could be fully EINTR-proof, so better to
use SA_RESTART always and deal with the implications of that. One such
implication is that we should not assume pg_usleep() will be terminated
early by a signal. Therefore, long sleeps should probably be replaced
by WaitLatch operations where practical.
Back-patch to 9.3 so we can get some beta testing on this change.
src/port/README
libpgport
=========
libpgport must have special behavior. It supplies functions to both
libraries and applications. However, there are two complexities:
1) Libraries need to use object files that are compiled with exactly
the same flags as the library. libpgport might not use the same flags,
so it is necessary to recompile the object files for individual
libraries. This is done by removing -lpgport from the link line:
# Need to recompile any libpgport object files
LIBS := $(filter-out -lpgport, $(LIBS))
and adding infrastructure to recompile the object files:
OBJS= execute.o typename.o descriptor.o data.o error.o prepare.o memory.o \
connect.o misc.o path.o exec.o \
$(filter snprintf.o, $(LIBOBJS))
The problem is that there is no testing of which object files need to be
added, but missing functions usually show up when linking user
applications.
2) For applications, we use -lpgport before -lpq, so the static files
from libpgport are linked first. This avoids having applications
dependent on symbols that are _used_ by libpq, but not intended to be
exported by libpq. libpq's libpgport usage changes over time, so such a
dependency is a problem. Win32, Linux, and Darwin use an export list to
control the symbols exported by libpq.
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