[ubsan] Make suppressions.cpp test pass for me on Windows

The test seems to be failing because the module suppression file
contains a colon. I found that it was sufficient to just use the
basename of the suppression file.

While I was here, I noticed that we don't implement IsAbsolutePath for
Windows, so I added it.

llvm-svn: 352921

compiler-rt/lib/sanitizer_common/sanitizer_win.cc

@@ -486,8 +486,14 @@ bool IsPathSeparator(const char c) {
   return c == '\\' || c == '/';
 }
 
+static bool IsAlpha(char c) {
+  c = ToLower(c);
+  return c >= 'a' && c <= 'z';
+}
+
 bool IsAbsolutePath(const char *path) {
-  UNIMPLEMENTED();
+  return path != nullptr && IsAlpha(path[0]) && path[1] == ':' &&
+         IsPathSeparator(path[2]);
 }
 
 void SleepForSeconds(int seconds) {

compiler-rt/test/ubsan/TestCases/Integer/suppressions.cpp

@@ -15,7 +15,10 @@
 
 // RUN: echo "unsigned-integer-overflow:do_overflow" > %t.func-supp
 // RUN: %env_ubsan_opts=halt_on_error=1:suppressions='"%t.func-supp"' %run %t
-// RUN: echo "unsigned-integer-overflow:%t" > %t.module-supp
+// FIXME: The '%t' substitution can't be used for the module name because it
+// contains a colon, so we have to use the basename, which is
+// suppressions.cpp.tmp.
+// RUN: echo "unsigned-integer-overflow:suppressions.cpp.tmp" > %t.module-supp
 // RUN: %env_ubsan_opts=halt_on_error=1:suppressions='"%t.module-supp"' %run %t
 
 // Note: file-level suppressions should work even without debug info.