fix(build): problem with reading LEAN_PATH on cygwin

Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>

src/CMakeLists.txt

@@ -30,6 +30,10 @@ if((${CYGWIN} EQUAL "1") OR (${CMAKE_SYSTEM_NAME} MATCHES "Windows"))
   set(LEAN_EXTRA_CXX_FLAGS "${LEAN_EXTRA_CXX_FLAGS} -D LEAN_WINDOWS -D LEAN_WIN_STACK_SIZE=${LEAN_WIN_STACK_SIZE}")
 endif()
 
+if("${CYGWIN}" EQUAL "1")
+  set(LEAN_EXTRA_CXX_FLAGS "${LEAN_EXTRA_CXX_FLAGS} -D LEAN_CYGWIN")
+endif()
+
 if("${MULTI_THREAD}" MATCHES "OFF")
   message(STATUS "Disabled multi-thread support, it will not be safe to run multiple threads in parallel")
 else()

src/util/lean_path.cpp

@@ -66,11 +66,51 @@ static std::string get_exe_location() {
 }
 #endif
 
+#if defined(LEAN_CYGWIN)
+/**
+   \brief Cleanup path when using cygwin.
+   This procedure performs two fixes, if the string contains '/'.
+
+   1- It replaces '/' with '\\' and ':' with ';'
+
+   2- Then, it replaces "\cygdrive\c\" with "c:"
+*/
+static std::string fix_cygwin_path(std::string f) {
+    if (f.find('/') != std::string::npos) {
+        // Step 1.
+        for (auto & c : f) {
+            if (c == g_bad_sep)
+                c = g_sep;
+            else if (c == ':')
+                c = g_path_sep;
+        }
+        // Step 2.
+        size_t pos = 0;
+        size_t matchpos;
+        std::string cygdrive("\\cygdrive\\");
+        while ((matchpos = f.find(cygdrive, pos)) != std::string::npos) {
+            // erase "\cygdrive\"
+            f = f.replace(matchpos, cygdrive.size(), "");
+            // replace the next "\" with ":\"
+            if ((matchpos = f.find("\\", matchpos)) != std::string::npos) {
+                f.replace(matchpos, 1, ":\\");
+            }
+            pos = matchpos;
+        }
+    }
+    return f;
+}
+#endif
+
 std::string normalize_path(std::string f) {
+#if defined(LEAN_CYGWIN)
+    f = fix_cygwin_path(f);
+#else
     for (auto & c : f) {
         if (c == g_bad_sep)
             c = g_sep;
     }
+#endif
     return f;
 }