This facility allowed us to build tcmalloc without linking in actual
-lpthread. Via weak symbols we checked at runtime if pthread functions
are available and if not, special single-threaded stubs were used
instead. Not always brining in pthread dependency helped performance
of some programs or libraries which depended at runtime on whether
threads are linked or not. Most notable of those are libstdc++ which
uses non-atomic refcounting on single threaded programs.
But such optional dependency on pthreads caused complications for
nearly no benefit. One trouble was reported in github issue #1110.
This days glibc/libstdc++ combo actually depends on
sys/single_threaded.h facility. So bringing pthread at runtime is
fine. Also modern glibc ships pthread symbols inside libc anyways and
libpthread is empty. I also found that for whatever reason on BSDs and
osx we already pulled in proper pthreads too.
So we loose nothing and we get issue #1110 fixed. And we simplify
everything.
This fixes issue #1371
From time to time things file inside tcmalloc guts where calling to
malloc is not safe. Regular strerror does locale bits, so will
occasionally open files/malloc/etc. We avoid this by using our own
"safe" variant that hardcodes names of all POSIX errno constants.
We previously tested wrong assumption that larger than page size size
classes have addresses aligned on page size. New code is making proper
check of size class.
Also added is unit test coverage for this previously failing
condition. And we now also run "assert-ful" unittests for big tcmalloc
too, not only tcmalloc_minimal configuration.
This fixes github issue #1254
Everyone should be using golang pprof from github.com/google/pprof, but
distros still ship our perl version and not everyone is aware of
better pprof yet.
This is another step in completely dropping perl pprof. We still
default to installing it, but hopefully we'll be able to convince
distros to disable this soon.
We still install pprof under pprof-symbolize name because
stack traces symbolization depends on it, and because golang pprof
won't support this feature.
This is related to issue #1038.
While this is not good representation of real-world production malloc
behavior, it is representative of length (instruction-wise and well as
cycle-wise) of fast-path. So this is better than nothing.
