[compiler-rt] Fix interception of multiple defined symbols.

[etienneb]

Summary

The MSVC compiler is generating multiple instance of the exception handler
when compiling on win64 with /MD.

see: https://msdn.microsoft.com/en-us/library/2kzt1wy3.aspx

Two tests were failing when running:

ninja check-asan-dynamic.

The tests were failing because only the first occurence of the function was patched.
The function __C_specific_handler is defined in ntdll and vcruntime140.

After this patch, there is still two remaining tests failing.

********************
Testing: 0 .. 10.. 20.. 30.. 40.. 50.. 60.. 70.. 80.. 90..
Testing Time: 87.81s
********************
Failing Tests (2):
    AddressSanitizer-x86_64-windows-dynamic :: TestCases/Windows/dll_intercept_memchr.cc
    AddressSanitizer-x86_64-windows-dynamic :: TestCases/Windows/dll_intercept_memcpy_indirect.cc

  Expected Passes    : 342
  Passes With Retry  : 2
  Expected Failures  : 16
  Unsupported Tests  : 152
  Unexpected Failures: 2

[etienneb]

fix coding style

[vitalybuka]

lib/interception/interception_win.cc

925

if (func_addr &&

[vitalybuka]

maybe explicit test for this case can be useful

[etienneb]

In D24983#555642, @vitalybuka wrote:

maybe explicit test for this case can be useful

There is already two tests for it. They were broken on windows 64-bits.
Windows 64-bits is not yet officially supported by Asan and there is no build bots testing it (yet).

[etienneb]

fix bubak comments

lib/interception/interception_win.cc

if (!strcmp(func_name, name)) {
 
       return (uptr)(char *)func;
     }
   }
 
   return 0;
 }
 
-static bool GetFunctionAddressInDLLs(const char *func_name, uptr *func_addr) {
-  *func_addr = 0;
+bool OverrideFunction(
+    const char *func_name, uptr new_func, uptr *orig_old_func) {
+  bool hooked = false;
+  uptr func_addr = 0;
   void **DLLs = InterestingDLLsAvailable();
-  for (size_t i = 0; *func_addr == 0 && DLLs[i]; ++i)
-    *func_addr = InternalGetProcAddress(DLLs[i], func_name);
-  return (*func_addr != 0);
+  for (size_t i = 0; DLLs[i]; ++i) {
+    func_addr = InternalGetProcAddress(DLLs[i], func_name);
+    if (func_addr != 0 &&
+        OverrideFunction(func_addr, new_func, orig_old_func)) {
+      hooked = true;
     }
-
-bool OverrideFunction(const char *name, uptr new_func, uptr *orig_old_func) {
-  uptr orig_func;
-  if (!GetFunctionAddressInDLLs(name, &orig_func))
-    return false;
-  return OverrideFunction(orig_func, new_func, orig_old_func);
+  }
+  return hooked;
 }
 
 bool OverrideImportedFunction(const char *module_to_patch,
                               const char *imported_module,
                               const char *function_name, uptr new_function,
                               uptr *orig_old_func) {
   HMODULE module = GetModuleHandleA(module_to_patch);
   if (!module)