Hello!
My usage scenario is a big Windows application with a lot of dlls, some
of which use HDF5 library. HDF5 code uses Dynamically Loaded Plugin Filters:
https://support.hdfgroup.org/HDF5/doc1.8/Advanced/DynamicallyLoadedFilters/HDF5DynamicallyLoadedFilters.pdf
The filters are deployed in a local directory which is activated via
modifying process HDF5_PLUGIN_PATH env.variable, just prior to loading
the library. That works fine, and important thing is that user can just
drop new plugins in that directory to support newer files.
However, it appears that in some cases plugin search fails. HDF5 library
retrieves HDF5_PLUGIN_PATH via
HDgetenv
which is defined as
#define HDgetenv(S) getenv(S)
According to
http://stackoverflow.com/questions/10636768/does-getenv-cache-the-result/10636993#10636993
"A process inherits the environment from the process creating the new
process. This is held in memory."
In the application I do not use C runtime (the implementation language
is not C), so I use SetEnvironmentVariable:
https://msdn.microsoft.com/ru-ru/library/windows/desktop/ms686206(v=vs.85).aspx
It appears that if I modify HDF5_PLUGIN_PATH before C runtime is loaded
for the first time in the application, all is fine. However if I call
SetEnvironmentVariable after C runtime is already loaded, it has no
effect for HDF5.
The application is huge, and it's very hard to control the moments C
runtime and HDF5 library are loaded. I wonder -- does it make sense to
add HDF5 procedures to verbosely modify plugin search path, something like
herr_t H5PLadd_path(const char *name)
herr_t H5PLrem_path(const char *name)
?
The above procedures could use HDsetenv, which is otherwise not
accessible (from non-C applications).
(I think similar motivation led to exposing H5free_memory procedure.)
What do you think?
Best wishes,
Andrey Paramonov
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