[clang] 0f73a24 - [clang][Sema] Skip access check on arrays of zero-length element

[via cfe-commits]

Author: dingfei
Date: 2023-08-11T22:05:04+08:00
New Revision: 0f73a2406a16f3a69dd6e62f0faa3a4aa05c5d84

URL: https://github.com/llvm/llvm-project/commit/0f73a2406a16f3a69dd6e62f0faa3a4aa05c5d84
DIFF: https://github.com/llvm/llvm-project/commit/0f73a2406a16f3a69dd6e62f0faa3a4aa05c5d84.diff

LOG: [clang][Sema] Skip access check on arrays of zero-length element

Bound check on array of zero-sized element isn't meaningful.

Fixes https://github.com/llvm/llvm-project/issues/64564

Reviewed By: jacquesguan

Differential Revision: https://reviews.llvm.org/D157584

Added: 
    clang/test/Sema/array-bounds-zero-length-elem-gh64564.c

Modified: 
    clang/docs/ReleaseNotes.rst
    clang/lib/Sema/SemaChecking.cpp

Removed: 
    


################################################################################
diff  --git a/clang/docs/ReleaseNotes.rst b/clang/docs/ReleaseNotes.rst
index c438db074a19b7..a80f57d9bb71ac 100644
--- a/clang/docs/ReleaseNotes.rst
+++ b/clang/docs/ReleaseNotes.rst
@@ -185,6 +185,8 @@ Miscellaneous Clang Crashes Fixed
   terminated. Clang should now also recover better when an @end is missing
   between blocks.
   `Issue 64065 <https://github.com/llvm/llvm-project/issues/64065>`_
+- Fixed a crash when check array access on zero-length element.
+  `Issue 64564 <https://github.com/llvm/llvm-project/issues/64564>`_
 
 Target Specific Changes
 -----------------------

diff  --git a/clang/lib/Sema/SemaChecking.cpp b/clang/lib/Sema/SemaChecking.cpp
index 09696ee73ca38c..984e43c1fcfad5 100644
--- a/clang/lib/Sema/SemaChecking.cpp
+++ b/clang/lib/Sema/SemaChecking.cpp
@@ -17146,7 +17146,7 @@ void Sema::CheckArrayAccess(const Expr *BaseExpr, const Expr *IndexExpr,
           ASTC.getTypeSizeInCharsIfKnown(EffectiveType);
       // PR50741 - If EffectiveType has unknown size (e.g., if it's a void
       // pointer) bounds-checking isn't meaningful.
-      if (!ElemCharUnits)
+      if (!ElemCharUnits || ElemCharUnits->isZero())
         return;
       llvm::APInt ElemBytes(index.getBitWidth(), ElemCharUnits->getQuantity());
       // If index has more active bits than address space, we already know

diff  --git a/clang/test/Sema/array-bounds-zero-length-elem-gh64564.c b/clang/test/Sema/array-bounds-zero-length-elem-gh64564.c
new file mode 100644
index 00000000000000..1aaf01d82011bc
--- /dev/null
+++ b/clang/test/Sema/array-bounds-zero-length-elem-gh64564.c
@@ -0,0 +1,12 @@
+// RUN: %clang_cc1 -triple i686-apple-darwin -verify %s
+
+int a[][0]; // expected-warning {{tentative array definition assumed to have one element}}
+void gh64564_1(void) {
+  int b = a[0x100000000][0];
+}
+
+typedef struct {} S;
+S s[]; // expected-warning {{tentative array definition assumed to have one element}}
+void gh64564_2(void) {
+  S t = s[0x100000000];
+}