[llvm] [MCParser] Fix some bound checking when scanning macro body (PR #219367)

[Fangrui Song via llvm-commits]

https://github.com/MaskRay created https://github.com/llvm/llvm-project/pull/219367

None

>From 1d86db75d61ba4e829847b856ccc482528f01e4f Mon Sep 17 00:00:00 2001
From: Fangrui Song <i at maskray.me>
Date: Thu, 27 Aug 2026 21:50:32 -0700
Subject: [PATCH] [MCParser] Fix some bound checking when scanning macro body

---
 llvm/lib/MC/MCParser/AsmParser.cpp | 10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

diff --git a/llvm/lib/MC/MCParser/AsmParser.cpp b/llvm/lib/MC/MCParser/AsmParser.cpp
index 320a3d896e9d0..839dbca990578 100644
--- a/llvm/lib/MC/MCParser/AsmParser.cpp
+++ b/llvm/lib/MC/MCParser/AsmParser.cpp
@@ -2519,7 +2519,7 @@ bool AsmParser::expandMacro(raw_svector_ostream &OS, MCAsmMacro &Macro,
         I += 2;
         continue;
       }
-      if (Body[I + 1] == '(' && Body[I + 2] == ')') {
+      if (Body[I + 1] == '(' && I + 2 != End && Body[I + 2] == ')') {
         I += 3;
         continue;
       }
@@ -2577,7 +2577,7 @@ bool AsmParser::expandMacro(raw_svector_ostream &OS, MCAsmMacro &Macro,
     }
 
     const size_t Start = I;
-    while (++I && isIdentifierChar(Body[I])) {
+    while (++I != End && isIdentifierChar(Body[I])) {
     }
     StringRef Token(Body.data() + Start, I - Start);
     if (AltMacroMode) {
@@ -4902,8 +4902,8 @@ void AsmParser::checkForBadMacro(SMLoc DirectiveLoc, StringRef Name,
       }
       Pos += 2;
     } else {
-      unsigned I = Pos + 1;
-      while (isIdentifierChar(Body[I]) && I + 1 != End)
+      size_t I = Pos + 1;
+      while (I != End && isIdentifierChar(Body[I]))
         ++I;
 
       const char *Begin = Body.data() + Pos + 1;
@@ -4914,7 +4914,7 @@ void AsmParser::checkForBadMacro(SMLoc DirectiveLoc, StringRef Name,
           break;
 
       if (Index == NParameters) {
-        if (Body[Pos + 1] == '(' && Body[Pos + 2] == ')')
+        if (Body[Pos + 1] == '(' && Pos + 2 != End && Body[Pos + 2] == ')')
           Pos += 3;
         else {
           Pos = I;