[PATCH] D158557: [clang] Fix crash in __builtin_strncmp and other related builtin functions

[Shafik Yaghmour via Phabricator via cfe-commits]

shafik created this revision.
shafik added reviewers: aaron.ballman, erichkeane, davide, rsmith.
Herald added a project: All.
shafik requested review of this revision.

The implementation of `__builtin_strncmp` and other related builtins function 
use `getExtValue()` to evaluate the size argument. This can cause a crash when 
the value does not fit into an `int64_t` value, which is can be expected since 
the type of the argument is `size_t`.

The fix is to switch to using `getZExtValue()`.

This fixes:

https://github.com/llvm/llvm-project/issues/64876


https://reviews.llvm.org/D158557

Files:
  clang/lib/AST/ExprConstant.cpp
  clang/test/SemaCXX/constexpr-string.cpp


Index: clang/test/SemaCXX/constexpr-string.cpp
===================================================================
--- clang/test/SemaCXX/constexpr-string.cpp
+++ clang/test/SemaCXX/constexpr-string.cpp
@@ -676,3 +676,14 @@
   }
   static_assert(test_address_of_incomplete_struct_type()); // expected-error 
{{constant}} expected-note {{in call}}
 }
+
+namespace GH64876 {
+void f() {
+  __builtin_strncmp(0, 0, -511LL);
+  __builtin_memcmp(0, 0, -511LL);
+  __builtin_bcmp(0, 0, -511LL);
+  __builtin_wmemcmp(0, 0, -511LL);
+  __builtin_memchr((const void*)0, 1, -511LL);
+  __builtin_wmemchr((const wchar_t*)0, 1, -511LL);
+}
+}
Index: clang/lib/AST/ExprConstant.cpp
===================================================================
--- clang/lib/AST/ExprConstant.cpp
+++ clang/lib/AST/ExprConstant.cpp
@@ -9357,7 +9357,7 @@
       APSInt N;
       if (!EvaluateInteger(E->getArg(2), N, Info))
         return false;
-      MaxLength = N.getExtValue();
+      MaxLength = N.getZExtValue();
     }
     // We cannot find the value if there are no candidates to match against.
     if (MaxLength == 0u)
@@ -12381,7 +12381,7 @@
       APSInt N;
       if (!EvaluateInteger(E->getArg(2), N, Info))
         return false;
-      MaxLength = N.getExtValue();
+      MaxLength = N.getZExtValue();
     }
 
     // Empty substrings compare equal by definition.



Index: clang/test/SemaCXX/constexpr-string.cpp
===================================================================
--- clang/test/SemaCXX/constexpr-string.cpp
+++ clang/test/SemaCXX/constexpr-string.cpp
@@ -676,3 +676,14 @@
   }
   static_assert(test_address_of_incomplete_struct_type()); // expected-error {{constant}} expected-note {{in call}}
 }
+
+namespace GH64876 {
+void f() {
+  __builtin_strncmp(0, 0, -511LL);
+  __builtin_memcmp(0, 0, -511LL);
+  __builtin_bcmp(0, 0, -511LL);
+  __builtin_wmemcmp(0, 0, -511LL);
+  __builtin_memchr((const void*)0, 1, -511LL);
+  __builtin_wmemchr((const wchar_t*)0, 1, -511LL);
+}
+}
Index: clang/lib/AST/ExprConstant.cpp
===================================================================
--- clang/lib/AST/ExprConstant.cpp
+++ clang/lib/AST/ExprConstant.cpp
@@ -9357,7 +9357,7 @@
       APSInt N;
       if (!EvaluateInteger(E->getArg(2), N, Info))
         return false;
-      MaxLength = N.getExtValue();
+      MaxLength = N.getZExtValue();
     }
     // We cannot find the value if there are no candidates to match against.
     if (MaxLength == 0u)
@@ -12381,7 +12381,7 @@
       APSInt N;
       if (!EvaluateInteger(E->getArg(2), N, Info))
         return false;
-      MaxLength = N.getExtValue();
+      MaxLength = N.getZExtValue();
     }
 
     // Empty substrings compare equal by definition.

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