revert to using lib_ptr, but discover it automatically

Author: Christopher Rowley

src/C/context.jl

@@ -103,14 +103,44 @@ Execute `f()` on the main thread.
 on_main_thread
 
 
+function find_lib_ptr()
+    # borrowed from PyCall.jl/src/startup.jl
+    @static if Sys.iswindows()
+        EnumProcessModules(hProcess, lphModule, cb, lpcbNeeded) =
+            ccall(:K32EnumProcessModules, stdcall, Bool,
+                (Ptr{Cvoid}, Ptr{Ptr{Cvoid}}, UInt32, Ptr{UInt32}),
+                hProcess, lphModule, cb, lpcbNeeded)
+
+        lpcbneeded = Ref{UInt32}()
+        proc_handle = ccall(:GetCurrentProcess, stdcall, Ptr{Cvoid}, ())
+        handles = Vector{Ptr{Cvoid}}(undef, 20)
+        if EnumProcessModules(proc_handle, handles, sizeof(handles), lpcbneeded) == 0
+            resize!(handles, div(lpcbneeded[],sizeof(Ptr{Cvoid})))
+            if EnumProcessModules(proc_handle, handles, sizeof(handles), lpcbneeded) == 0
+                error()
+            end
+        end
+        for handle in handles
+            if ccall(:GetProcAddress, stdcall, Ptr{Cvoid},
+                (Ptr{Cvoid}, Ptr{UInt8}), handle, "Py_GetVersion") != C_NULL
+                return handle
+            end
+        end
+        error("could not find libpython handle")
+    else
+        return unsafe_load(cglobal(:jl_exe_handle, Ptr{Cvoid}))
+    end
+end
+
+
 function init_context()
 
     CTX.is_embedded = hasproperty(Base.Main, :__PythonCall_embedded__)
 
     if CTX.is_embedded
         # In this case, getting a handle to libpython is easy
-        CTX.lib_ptr = C_NULL
-        init_pointers(true)
+        CTX.lib_ptr = find_lib_ptr()
+        init_pointers()
         # Check Python is initialized
         Py_IsInitialized() == 0 && error("Python is not already initialized.")
         CTX.is_initialized = true
@@ -236,7 +266,7 @@ function init_context()
         end
 
         # Get function pointers from the library
-        init_pointers(false)
+        init_pointers()
 
         # Initialize the interpreter
         CTX.is_preinitialized = Py_IsInitialized() != 0

src/C/pointers.jl

@@ -282,29 +282,19 @@ end
 
 const POINTERS = CAPIPointers()
 
-function _dlsym(lib::Ptr{Cvoid}, sym::Symbol)
-    if lib == C_NULL
-        # embedded case, python symbols available globally
-        cglobal(sym)::Ptr{Cvoid}
-    else
-        dlsym(lib, sym)::Ptr{Cvoid}
-    end
-end
-
-@eval function init_pointers(embedded::Bool, p::CAPIPointers = POINTERS, lib::Ptr = CTX.lib_ptr)
-    @assert (lib == C_NULL) == embedded
+@eval function init_pointers(p::CAPIPointers = POINTERS, lib::Ptr = CTX.lib_ptr)
     $([
-        :(p.$name = _dlsym(lib, $(QuoteNode(name))))
+        :(p.$name = dlsym(lib, $(QuoteNode(name))))
         for name in CAPI_FUNCS
     ]...)
     $(
         [
             :(p.$name =
-                    Base.unsafe_load(Ptr{PyPtr}(_dlsym(lib, $(QuoteNode(name)))::Ptr))) for name in CAPI_EXCEPTIONS
+                    Base.unsafe_load(Ptr{PyPtr}(dlsym(lib, $(QuoteNode(name)))::Ptr))) for name in CAPI_EXCEPTIONS
         ]...
     )
-    $([:(p.$name = _dlsym(lib, $(QuoteNode(name)))) for name in CAPI_OBJECTS]...)
-    p.PyOS_InputHookPtr = _dlsym(CTX.lib_ptr, :PyOS_InputHook)
+    $([:(p.$name = dlsym(lib, $(QuoteNode(name)))) for name in CAPI_OBJECTS]...)
+    p.PyOS_InputHookPtr = dlsym(CTX.lib_ptr, :PyOS_InputHook)
     nothing
 end