[clang] Clang/Preprocessor: Support short circuit in directive (PR #123912)

[via cfe-commits]

llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-clang

Author: YunQiang Su (wzssyqa)

<details>
<summary>Changes</summary>

Don't Evaluate RHS in if directive when short circuit. Examples include
   #if 0 &amp;&amp; another_condition
   #if 1 || another_condition

---
Full diff: https://github.com/llvm/llvm-project/pull/123912.diff


2 Files Affected:

- (modified) clang/lib/Lex/PPExpressions.cpp (+27-1) 
- (added) clang/test/Preprocessor/directive-short-circuit.c (+74) 


``````````diff
diff --git a/clang/lib/Lex/PPExpressions.cpp b/clang/lib/Lex/PPExpressions.cpp
index a3b1384f0fa1d6..7e413ec6076642 100644
--- a/clang/lib/Lex/PPExpressions.cpp
+++ b/clang/lib/Lex/PPExpressions.cpp
@@ -624,7 +624,33 @@ static bool EvaluateDirectiveSubExpr(PPValue &LHS, 
unsigned MinPrec,
 
     // Consume the operator, remembering the operator's location for reporting.
     SourceLocation OpLoc = PeekTok.getLocation();
-    PP.LexNonComment(PeekTok);
+
+    if (!RHSIsLive && (Operator == tok::ampamp || Operator == tok::pipepipe)) {
+      unsigned ThisPrec = PeekPrec;
+      while (true) {
+        PP.LexUnexpandedNonComment(PeekTok);
+        if (PeekTok.is(tok::l_paren)) {
+          unsigned NestParen = 1;
+          while (true) {
+            PP.LexUnexpandedNonComment(PeekTok);
+            if (PeekTok.is(tok::l_paren))
+              NestParen++;
+            else if (PeekTok.is(tok::r_paren))
+              NestParen--;
+            if (NestParen == 0)
+              break;
+          }
+          PP.LexUnexpandedNonComment(PeekTok);
+        }
+        PeekPrec = getPrecedence(PeekTok.getKind());
+        if (PeekPrec <= ThisPrec) {
+          LHS.setEnd(PeekTok.getEndLoc());
+          break;
+        }
+      }
+      continue;
+    } else
+      PP.LexNonComment(PeekTok);
 
     PPValue RHS(LHS.getBitWidth());
     // Parse the RHS of the operator.
diff --git a/clang/test/Preprocessor/directive-short-circuit.c 
b/clang/test/Preprocessor/directive-short-circuit.c
new file mode 100644
index 00000000000000..d137f8198cbbcf
--- /dev/null
+++ b/clang/test/Preprocessor/directive-short-circuit.c
@@ -0,0 +1,74 @@
+// RUN: %clang -E -MD -MF - %s | FileCheck -check-prefix ZERO_AND_HAS_INCLUDE 
%s
+//
+// ZERO_AND_HAS_INCLUDE-NOT: limits.h
+//
+#if 0 && __has_include(<limits.h>)
+#include <limits.h>
+#endif
+
+#if 4==5 && __has_include(<limits.h>)
+#include <limits.h>
+#endif
+
+#if defined(_THIS_IS_NOT_DEFINED) && __has_include(<limits.h>)
+#include <limits.h>
+#endif
+
+#if 0 && (__has_include(<limits.h>))
+#include <limits.h>
+#endif
+
+#if 4==5 && (__has_include(<limits.h>))
+#include <limits.h>
+#endif
+
+#if defined(_THIS_IS_NOT_DEFINED) && (__has_include(<limits.h>))
+#include <limits.h>
+#endif
+
+#if 0 && (5==5 && __has_include(<limits.h>))
+#include <limits.h>
+#endif
+
+#if 1 && (4==5 && __has_include(<limits.h>))
+#include <limits.h>
+#endif
+
+
+
+
+
+
+#if 1 || __has_include(<limits.h>)
+XXXXXXXXXX
+#endif
+#if 5==5 || __has_include(<limits.h>)
+XXXXXXXXXX
+#endif
+
+#if defined(__clang__) || __has_include(<limits.h>)
+XXXXXXXXXX
+#endif
+
+#if 1 || (__has_include(<limits.h>))
+#endif
+
+#if 5==5 || (__has_include(<limits.h>))
+XXXXXXXXXX
+#endif
+
+#if defined(__clang__) || (__has_include(<limits.h>))
+XXXXXXXXXX
+#endif
+
+#if 1 && (5==5 || __has_include(<limits.h>))
+XXXXXXXXXX
+#endif
+
+#if 1 || (5==5 || __has_include(<limits.h>))
+XXXXXXXXXX
+#endif
+
+#if 0 || (5==5 || __has_include(<limits.h>))
+XXXXXXXXXX
+#endif

``````````

</details>


https://github.com/llvm/llvm-project/pull/123912
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