Improve handling of compound format specifiers in Natvis

src/MIDebugEngine/Engine.Impl/Variables.cs

@@ -389,10 +389,16 @@ private string ProcessFormatSpecifiers(string exp, out string formatSpecifier)
             if (lastComma <= 0)
                 return exp;
 
+            // Find the format specifier expression
+            string expFS = exp.Substring(lastComma + 1).Trim();
+
+            // Strip off modifiers that may be included together with another format specifier, e.g. 'nvoXb' is a valid format specifier, but we only care about the 'Xb' part
+            // This is not quite the right fix -- really the below switch statement should be a series of if statements. But since none of the supported format specifiers
+            // contain any of these characters we can fix this the simple way and remove them.
+            expFS = expFS.Replace("nvo", "").Replace("na", "").Replace("nr", "").Replace("nd", "");
+
             // https://docs.microsoft.com/en-us/visualstudio/debugger/format-specifiers-in-cpp
-            string expFS = exp.Substring(lastComma + 1);
-            string trimmed = expFS.Trim();
-            switch (trimmed)
+            switch (expFS)
             {
                 case "x":
                 case "X":
@@ -433,19 +439,17 @@ private string ProcessFormatSpecifiers(string exp, out string formatSpecifier)
                     return "(char)(" + exp.Substring(0, lastComma) + ")";
                 // just remove and ignore these
                 case "en":
-                case "na":
-                case "nd":
-                case "nr":
                 case "!":
                 case "":
                     return exp.Substring(0, lastComma);
             }
 
-            // array with static size
-            var m = Regex.Match(trimmed, @"^\[?(\d+)\]?$");
-            if (m.Success)
+            // Array with static size
+            // Note that size specifiers may also include format specifiers (e.g. "ptr,[10]s8") which we should recognize in the regex, but ignore, since neither LLDB nor GDB support them
+            var matchStatic = Regex.Match(expFS, @"^\[?(\d+)\]?[a-zA-Z\d]*$");
+            if (matchStatic.Success)
             {
-                string count = m.Groups[1].Value; // (\d+) capture group
+                string count = matchStatic.Groups[1].Value; // (\d+) capture group
                 string expr = exp.Substring(0, lastComma);
 
                 if (_engine.DebuggedProcess.MICommandFactory.Mode == MIMode.Gdb)
@@ -472,9 +476,13 @@ private string ProcessFormatSpecifiers(string exp, out string formatSpecifier)
                 }
             }
 
-            // array with dynamic size
-            if (Regex.Match(trimmed, @"^\[([a-zA-Z_][a-zA-Z_\d]*)\]$").Success)
-                return exp.Substring(0, lastComma);
+            // Array with dynamic size is not supported, discard the format specifier
+            var matchDynamic = Regex.Match(expFS, @"^\[.*\][a-zA-Z\d]*$");
+            if (matchDynamic.Success)
+            {
+                string expr = exp.Substring(0, lastComma);
+                return expr;
+            }
 
             return exp;
         }