From 221514efe92676ce84a5e21bea91d8a6b21f9ed7 Mon Sep 17 00:00:00 2001
From: Kevin Enderby <enderby@apple.com>
Date: Tue, 22 Jan 2013 21:44:53 +0000
Subject: Add a warning when there is a macro defintion that has named
 parameters but the body does not use them and it appears the body has
 positional parameters.

This can cause unexpected results as in the added test case.  As the darwin
version of gas(1) which only supported positional parameters, happened to
ignore the named parameters.  Now that we want to support both styles of
macros we issue a warning in this specific case.

rdar://12861644


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@173199 91177308-0d34-0410-b5e6-96231b3b80d8
---
 lib/MC/MCParser/AsmParser.cpp | 104 ++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 104 insertions(+)

(limited to 'lib/MC/MCParser/AsmParser.cpp')

diff --git a/lib/MC/MCParser/AsmParser.cpp b/lib/MC/MCParser/AsmParser.cpp
index b5f51d8484..4d6756e1b6 100644
--- a/lib/MC/MCParser/AsmParser.cpp
+++ b/lib/MC/MCParser/AsmParser.cpp
@@ -237,6 +237,8 @@ private:
   void EatToEndOfLine();
   bool ParseCppHashLineFilenameComment(const SMLoc &L);
 
+  void CheckForBadMacro(SMLoc DirectiveLoc, StringRef Name, StringRef Body,
+                        MCAsmMacroParameters Parameters);
   bool expandMacro(raw_svector_ostream &OS, StringRef Body,
                    const MCAsmMacroParameters &Parameters,
                    const MCAsmMacroArguments &A,
@@ -3044,10 +3046,112 @@ bool AsmParser::ParseDirectiveMacro(SMLoc DirectiveLoc) {
   const char *BodyStart = StartToken.getLoc().getPointer();
   const char *BodyEnd = EndToken.getLoc().getPointer();
   StringRef Body = StringRef(BodyStart, BodyEnd - BodyStart);
+  CheckForBadMacro(DirectiveLoc, Name, Body, Parameters);
   DefineMacro(Name, MCAsmMacro(Name, Body, Parameters));
   return false;
 }
 
+/// CheckForBadMacro
+///
+/// With the support added for named parameters there may be code out there that
+/// is transitioning from positional parameters.  In versions of gas that did
+/// not support named parameters they would be ignored on the macro defintion.
+/// But to support both styles of parameters this is not possible so if a macro
+/// defintion has named parameters but does not use them and has what appears
+/// to be positional parameters, strings like $1, $2, ... and $n, then issue a
+/// warning that the positional parameter found in body which have no effect.
+/// Hoping the developer will either remove the named parameters from the macro
+/// definiton so the positional parameters get used if that was what was
+/// intended or change the macro to use the named parameters.  It is possible
+/// this warning will trigger when the none of the named parameters are used
+/// and the strings like $1 are infact to simply to be passed trough unchanged.
+void AsmParser::CheckForBadMacro(SMLoc DirectiveLoc, StringRef Name,
+                                 StringRef Body,
+                                 MCAsmMacroParameters Parameters) {
+  // If this macro is not defined with named parameters the warning we are
+  // checking for here doesn't apply.
+  unsigned NParameters = Parameters.size();
+  if (NParameters == 0)
+    return;
+
+  bool NamedParametersFound = false;
+  bool PositionalParametersFound = false;
+
+  // Look at the body of the macro for use of both the named parameters and what
+  // are likely to be positional parameters.  This is what expandMacro() is
+  // doing when it finds the parameters in the body.
+  while (!Body.empty()) {
+    // Scan for the next possible parameter.
+    std::size_t End = Body.size(), Pos = 0;
+    for (; Pos != End; ++Pos) {
+      // Check for a substitution or escape.
+      // This macro is defined with parameters, look for \foo, \bar, etc.
+      if (Body[Pos] == '\\' && Pos + 1 != End)
+        break;
+
+      // This macro should have parameters, but look for $0, $1, ..., $n too.
+      if (Body[Pos] != '$' || Pos + 1 == End)
+        continue;
+      char Next = Body[Pos + 1];
+      if (Next == '$' || Next == 'n' || isdigit(Next))
+        break;
+    }
+
+    // Check if we reached the end.
+    if (Pos == End)
+      break;
+
+    if (Body[Pos] == '$') {
+      switch (Body[Pos+1]) {
+        // $$ => $
+      case '$':
+        break;
+
+        // $n => number of arguments
+      case 'n':
+        PositionalParametersFound = true;
+        break;
+
+        // $[0-9] => argument
+      default: {
+        PositionalParametersFound = true;
+        break;
+        }
+      }
+      Pos += 2;
+    } else {
+      unsigned I = Pos + 1;
+      while (isIdentifierChar(Body[I]) && I + 1 != End)
+        ++I;
+
+      const char *Begin = Body.data() + Pos +1;
+      StringRef Argument(Begin, I - (Pos +1));
+      unsigned Index = 0;
+      for (; Index < NParameters; ++Index)
+        if (Parameters[Index].first == Argument)
+          break;
+
+      if (Index == NParameters) {
+          if (Body[Pos+1] == '(' && Body[Pos+2] == ')')
+            Pos += 3;
+          else {
+            Pos = I;
+          }
+      } else {
+        NamedParametersFound = true;
+        Pos += 1 + Argument.size();
+      }
+    }
+    // Update the scan point.
+    Body = Body.substr(Pos);
+  }
+
+  if (!NamedParametersFound && PositionalParametersFound)
+    Warning(DirectiveLoc, "macro defined with named parameters which are not "
+                          "used in macro body, possible positional parameter "
+                          "found in body which will have no effect");
+}
+
 /// ParseDirectiveEndMacro
 /// ::= .endm
 /// ::= .endmacro
-- 
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