On Feb 5 21:41, Bruno Haible wrote: > Hi Corinna, > > Thanks for the heads-up and patch. > > > Note that dllimport/dllexport decorations are not at all required on > > Cygwin for quite some time. > > Is this true in all circumstances? I thought that when --disable-auto-import > is in use AND the shared library wants to export variables, dllimport > and dllexport decorations are necessary. > > > On Cygwin --export-all-symbols is default. However, if just a single > > symbol is decorated with dllexport, ld switches to exporting only these > > symbols. > > ... > > An example of that is current recode. Building this package with > > --enable-shared is broken, unless one adds -Wl,--export-all-symbols to > > the link stage command line explicitely, because of the decorated > > gl_get_setlocale_null_lock variable. > > So, there are three types of packages: > (A) Those that use --disable-auto-import (e.g. [1][2]) and provide an > explicit list of exports for their shared libraries. > (B) Those that don't use --disable-auto-import but want to limit > the exposed symbols for other reasons (e.g. namespace cleanliness). > Such as those that use the libtool options '-export-symbols' or > '-export-symbols-regex'. > (C) Those like 'recode', which want all symbols to be exported (e.g. > if namespace cleanliness is not an issue for them). > > For packages of type (A) or (B), the symbol gl_get_setlocale_null_lock > *MUST* be exported, otherwise there may be different get_setlocale_null_lock > functions accessed by different code, which will destroy the purpose of this > function, i.e. open the door to potential crashes due to use of setlocale(). > > For packages of type (C), the symbol gl_get_setlocale_null_lock *MUST NOT* > be exported, otherwise all other symbols will not be exported. > > AFAIU, your patch fixes packages of type (C), while at the same time breaking > packages of type (A) or (B). > > Is there an easy way to distinguish packages of type (C) from those of type > (A), (B)? > > Another option — since we are talking about a single symbol and a single > platform — would be if the locking for setlocale_null were not necessary > on Cygwin in the first place. I determined that it is necessary by running > the unit test gnulib/tests/test-setlocale_null-mt-all.c [3] on Cygwin: > without the lock, it crashed within less than 1 second. Could the > implementation of setlocale() in Cygwin be changed in such a way that this > test does not crash? Then the lock would be necessary.
Well, we could do that by adding Cygwin-internal locking to setlocale calls. But that would only be available in the next Cygwin version of course. May I ask what's the idea to provide a thread-safe setlocale? It was never defined as thread-safe and POSIX explicitely mentions that. Any application expecting to call setlocale thread-safe is broken by design. It should use the newlocale/duplocale/uselocale/freelocale API instead, isn't it? Corinna > > Bruno > > [1] > https://git.savannah.gnu.org/gitweb/?p=gettext.git;a=blob;f=gettext-tools/woe32dll/export.h;hb=HEAD > [2] https://haible.de/bruno/woe32dll.html > [3] > https://git.savannah.gnu.org/gitweb/?p=gnulib.git;a=blob;f=tests/test-setlocale_null-mt-all.c;hb=HEAD > >
