[windows] Fix self-path lookup on Windows (#103)

Store handle to self in `DllMain` so that we don't try to figure out a
handle to ourselves (incorrectly) anymore on Windows.

Add test for LBT path printing when `LBT_VERBOSE=1`

Author: staticfloat

src/dl_utils.c

@@ -82,10 +82,11 @@ void * lookup_symbol(const void * handle, const char * symbol_name) {
  * Work around protected symbol visibility and GCC/ld.bfd bug:
  * https://sourceware.org/bugzilla/show_bug.cgi?id=26815
  */
+extern void * _win32_self_handle;
 void * lookup_self_symbol(const char * symbol_name) {
     void * self_handle = NULL;
 #if defined(_OS_WINDOWS_)
-    self_handle = GetModuleHandle(NULL);
+    self_handle = _win32_self_handle;
 #elif defined(_OS_DARWIN_)
     self_handle = RTLD_SELF;
 #elif defined(RTLD_DEFAULT)
@@ -104,7 +105,7 @@ const char * lookup_self_path()
         return self_path;
     }
 #if defined(_OS_WINDOWS_)
-    if (!GetModuleFileNameA(GetModuleHandle(NULL), self_path, PATH_MAX)) {
+    if (!GetModuleFileNameA(_win32_self_handle, self_path, PATH_MAX)) {
         fprintf(stderr, "ERROR: GetModuleFileName() failed\n");
         strcpy(self_path, "<unknown>");
         return self_path;

src/libblastrampoline.c

@@ -395,8 +395,19 @@ LBT_DLLEXPORT int32_t lbt_forward(const char * libname, int32_t clear, int32_t v
     return nforwards;
 }
 
-
+/*
+ * On windows it's surprisingly difficult to get a handle to ourselves,
+ * and that's because they give it to you in `DllMain()`.  ;)
+ */
+#ifdef _OS_WINDOWS_
+void * _win32_self_handle;
+BOOL APIENTRY DllMain(HINSTANCE hModule, DWORD code, void *) {
+    if (code == DLL_PROCESS_ATTACH) {
+        _win32_self_handle = (void *)hModule;
+    }
+#else
 __attribute__((constructor)) void init(void) {
+#endif
     // Initialize config structures
     init_config();
 
@@ -457,4 +468,8 @@ __attribute__((constructor)) void init(void) {
             clear = 0;
         }
     }
+
+#ifdef _OS_WINDOWS_
+    return TRUE;
+#endif
 }

src/win_utils.c

@@ -31,4 +31,4 @@ int utf8_to_wchar(const char * str, wchar_t * wstr, size_t maxlen) {
     if (!MultiByteToWideChar(CP_UTF8, 0, str, -1, wstr, len))
         return 0;
     return 1;
-}
+}

test/runtests.jl

@@ -61,6 +61,13 @@ function run_test((test_name, test_expected_outputs, expect_success), libblas_na
         end
         @test expected_return_value
 
+        # Expect to see the path to `libblastrampoline` within the output,
+        # since we have `LBT_VERBOSE=1` and at startup, it announces its own path:
+        if startswith(libblas_name, "blastrampoline")
+            lbt_libdir = first(libdirs)
+            @test occursin(lbt_libdir, output)
+        end
+
         # Test to make sure the test ran properly
         has_expected_output = all(occursin(expected, output) for expected in test_expected_outputs)
         if !has_expected_output
@@ -187,7 +194,7 @@ end
 if openblas_interface == :ILP64
     inconsolable = ("inconsolable_test", ("||C||^2 is:  24.3384", "||b||^2 is:   3.0000"), true)
     @testset "LBT -> OpenBLAS 32 + 64 (LP64 + ILP64)" begin
-        libdirs = unique(vcat(OpenBLAS32_jll.LIBPATH_list..., OpenBLAS_jll.LIBPATH_list..., CompilerSupportLibraries_jll.LIBPATH_list..., lbt_dir))
+        libdirs = unique(vcat(lbt_dir, OpenBLAS32_jll.LIBPATH_list..., OpenBLAS_jll.LIBPATH_list..., CompilerSupportLibraries_jll.LIBPATH_list...))
         run_test(inconsolable, lbt_link_name, libdirs, :wild_sobbing, "$(OpenBLAS32_jll.libopenblas_path);$(OpenBLAS_jll.libopenblas_path)")
     end
 end