36 lines
1.7 KiB
ReStructuredText
36 lines
1.7 KiB
ReStructuredText
.. _env_vars:
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Environment Variables
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======================
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Certain environment variables can affect or tune the behavior of the
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library. The variables and their behavior are described here.
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* ``BOTAN_THREAD_POOL_SIZE`` controls the number of threads which will be
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created for a thread pool used for some purposes within the library. If not
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set, or set to 0, then it defaults to the number of CPUs available on the
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system. If it is set to the string "none" then the thread pool is disabled;
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instead all work passed to the thread pool will be executed immediately
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by the calling thread.
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As of version 3.2.0, on MinGW the thread pool is by default disabled, due to a
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bug which causes deadlock on application shutdown. Enabling the pool can be
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explicitly requested by setting ``BOTAN_THREAD_POOL_SIZE`` to an integer
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value.
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* ``BOTAN_MLOCK_POOL_SIZE`` controls the total amount of memory, in bytes, which
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will be locked in memory using ``mlock`` or ``VirtualLock`` and managed in a
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memory pool. This should be a multiple of the system page size. If set to
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``0``, then the memory pool is disabled.
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* ``BOTAN_FFI_PRINT_EXCEPTIONS`` if this variable is set (to any value), then
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if an exception is caught by the FFI layer, before returning an error code, it
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will print the text message of the exception to stderr. This is primarily
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intended for debugging.
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* ``BOTAN_CLEAR_CPUID``: this variable can be set to a comma-separated list of
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CPUID fields to ignore. For example setting ``BOTAN_CLEAR_CPUID=avx2,avx512``
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will cause AVX2 and AVX-512 codepaths to be avoided. Note that disabling basic
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features (notably NEON or SSE2/SSSE3) can cause other higher level features
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like AES-NI to also become disabled.
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