diff -Naur ccache-3.4.2.orig/src/ccache.c ccache-3.4.2/src/ccache.c
--- ccache-3.4.2.orig/src/ccache.c	2018-08-16 17:13:29.359895100 -0400
+++ ccache-3.4.2/src/ccache.c	2018-08-16 17:15:51.861247500 -0400
@@ -855,6 +855,13 @@
 			}
 			// p and q span the include file path.
 			char *inc_path = x_strndup(p, q - p);
+#ifdef _WIN32
+			// gcc-E [file.c] -g adds CWD with double forward slashes
+			// like:
+			// # 1 "C:\\msys64\\home\\user\\test//"
+			// double forward slashes should be replaced with simple slashes
+			str_replace(inc_path, "\\\\", "\\");
+#endif
 			if (!has_absolute_include_headers) {
 				has_absolute_include_headers = is_absolute_path(inc_path);
 			}
diff -Naur ccache-3.7.orig/src/ccache.h ccache-3.7/src/ccache.h
--- ccache-3.7.orig/src/ccache.h	2019-04-23 21:37:37.438109100 -0400
+++ ccache-3.7/src/ccache.h	2019-04-23 21:38:16.908721300 -0400
@@ -213,6 +213,7 @@
 char *read_text_file(const char *path, size_t size_hint);
 char *subst_env_in_string(const char *str, char **errmsg);
 void set_cloexec_flag(int fd);
+void str_replace(char *target, const char *needle, const char *replacement);
 double time_seconds(void);
 
 // ----------------------------------------------------------------------------
diff -Naur ccache-3.4.2.orig/src/util.c ccache-3.4.2/src/util.c
--- ccache-3.4.2.orig/src/util.c	2018-08-16 17:13:29.344270000 -0400
+++ ccache-3.4.2/src/util.c	2018-08-16 17:19:32.688548500 -0400
@@ -1097,6 +1097,13 @@
 	} else {
 		snprintf(ret, maxlen, "%s", path);
 		p = ret;
+
+		//replace forward slashes with backward slashes inplace
+		char *tmp;
+		for(tmp = p; *tmp; tmp++)	{
+			if(*tmp == '/')
+				*tmp = '\\';
+		}
 	}
 #else
 	// Yes, there are such systems. This replacement relies on the fact that when
@@ -1286,11 +1293,17 @@
 	const char *p1 = s1;
 	const char *p2 = s2;
 
+#ifndef _WIN32
+	char dirseparator = '/';
+#else
+	char dirseparator = '\\';
+#endif
+
 	while (*p1 && *p2 && *p1 == *p2) {
 		++p1;
 		++p2;
 	}
-	while ((*p1 && *p1 != '/') || (*p2 && *p2 != '/')) {
+	while ((*p1 && *p1 != dirseparator) || (*p2 && *p2 != dirseparator)) {
 		p1--;
 		p2--;
 	}
@@ -1688,3 +1701,36 @@
 	(void)fd;
 #endif
 }
+
+void str_replace(char *target, const char *needle, const char *replacement)
+{
+    char buffer[1024] = { 0 };
+    char *insert_point = &buffer[0];
+    const char *tmp = target;
+    size_t needle_len = strlen(needle);
+    size_t repl_len = strlen(replacement);
+
+    while (1) {
+        const char *p = strstr(tmp, needle);
+
+        // walked past last occurrence of needle; copy remaining part
+        if (p == NULL) {
+            strcpy(insert_point, tmp);
+            break;
+        }
+
+        // copy part before needle
+        memcpy(insert_point, tmp, p - tmp);
+        insert_point += p - tmp;
+
+        // copy replacement string
+        memcpy(insert_point, replacement, repl_len);
+        insert_point += repl_len;
+
+        // adjust pointers, move on
+        tmp = p + needle_len;
+    }
+
+    // write altered string back to target
+    strcpy(target, buffer);
+}