[Support] Lazy load of dbghlp.dll on Windows
This patch changes linkage with dbghlp.dll for clang from static (at load time)
to on demand (at the first use of required functions). Clang uses dbghlp.dll
only in minor use-cases. First of all in case of crash and in case of plugin load.
The dbghlp.dll library can be absent on system. In this case clang will fail
to load. With lazy load of dbghlp.dll clang can work even if dbghlp.dll
is not available.
Differential Revision: http://reviews.llvm.org/D10737
llvm-svn: 241271
diff --git a/llvm/lib/Support/Windows/DynamicLibrary.inc b/llvm/lib/Support/Windows/DynamicLibrary.inc
index 79d5f79..d38f197 100644
--- a/llvm/lib/Support/Windows/DynamicLibrary.inc
+++ b/llvm/lib/Support/Windows/DynamicLibrary.inc
@@ -23,14 +23,6 @@
#include <ntverp.h>
#endif
-#ifdef __MINGW32__
- #if (HAVE_LIBIMAGEHLP != 1)
- #error "libimagehlp.a should be present"
- #endif
-#else
- #pragma comment(lib, "dbghelp.lib")
-#endif
-
namespace llvm {
using namespace sys;
@@ -39,10 +31,21 @@
//=== and must not be UNIX code.
//===----------------------------------------------------------------------===//
+typedef BOOL (WINAPI *fpEnumerateLoadedModules)(HANDLE,PENUMLOADED_MODULES_CALLBACK64,PVOID);
+static fpEnumerateLoadedModules fEnumerateLoadedModules;
static DenseSet<HMODULE> *OpenedHandles;
+static bool loadDebugHelp(void) {
+ HMODULE hLib = ::LoadLibraryW(L"Dbghelp.dll");
+ if (hLib) {
+ fEnumerateLoadedModules = (fpEnumerateLoadedModules)
+ ::GetProcAddress(hLib, "EnumerateLoadedModules64");
+ }
+ return fEnumerateLoadedModules != 0;
+}
+
static BOOL CALLBACK
-ELM_Callback(WIN32_ELMCB_PCSTR ModuleName, ULONG_PTR ModuleBase,
+ELM_Callback(WIN32_ELMCB_PCSTR ModuleName, DWORD64 ModuleBase,
ULONG ModuleSize, PVOID UserContext) {
OpenedHandles->insert((HMODULE)ModuleBase);
return TRUE;
@@ -57,7 +60,14 @@
if (OpenedHandles == 0)
OpenedHandles = new DenseSet<HMODULE>();
- EnumerateLoadedModules(GetCurrentProcess(), ELM_Callback, 0);
+ if (!fEnumerateLoadedModules) {
+ if (!loadDebugHelp()) {
+ assert(false && "These APIs should always be available");
+ return DynamicLibrary();
+ }
+ }
+
+ fEnumerateLoadedModules(GetCurrentProcess(), ELM_Callback, 0);
// Dummy library that represents "search all handles".
// This is mostly to ensure that the return value still shows up as "valid".
return DynamicLibrary(&OpenedHandles);