[clang] [clang][analyzer] Move 'alpha.core.PointerSub' checker into 'core.PointerSub' (PR #107596)

via cfe-commits cfe-commits at lists.llvm.org
Fri Sep 6 07:49:26 PDT 2024


llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-clang-static-analyzer-1

Author: Balázs Kéri (balazske)

<details>
<summary>Changes</summary>

Checker was tested on 16 projects. The only results were the offset calculations that were considered as valid (faulty) cases already.
https://codechecker-demo.eastus.cloudapp.azure.com/Default/reports?run=vim_v8.2.1920_pointersub_c&is-unique=off&diff-type=New&checker-name=alpha.core.PointerSub
https://codechecker-demo.eastus.cloudapp.azure.com/Default/reports?run=protobuf_v3.13.0_pointersub_cpp&is-unique=off&diff-type=New&checker-name=alpha.core.PointerSub

---
Full diff: https://github.com/llvm/llvm-project/pull/107596.diff


6 Files Affected:

- (modified) clang/docs/analyzer/checkers.rst (+43-43) 
- (modified) clang/include/clang/StaticAnalyzer/Checkers/Checkers.td (+5-5) 
- (modified) clang/test/Analysis/analyzer-enabled-checkers.c (+1) 
- (modified) clang/test/Analysis/pointer-sub-notes.c (+1-1) 
- (modified) clang/test/Analysis/pointer-sub.c (+1-1) 
- (modified) clang/test/Analysis/std-c-library-functions-arg-enabled-checkers.c (+1) 


``````````diff
diff --git a/clang/docs/analyzer/checkers.rst b/clang/docs/analyzer/checkers.rst
index 847bf4baf74887..05e7b985d52cec 100644
--- a/clang/docs/analyzer/checkers.rst
+++ b/clang/docs/analyzer/checkers.rst
@@ -170,6 +170,49 @@ disable this behavior with the option
    obj->x = 1; // warn
  }
 
+.. _core-PointerSub:
+
+core.PointerSub (C)
+"""""""""""""""""""
+Check for pointer subtractions on two pointers pointing to different memory
+chunks. According to the C standard §6.5.6 only subtraction of pointers that
+point into (or one past the end) the same array object is valid (for this
+purpose non-array variables are like arrays of size 1). This checker only
+searches for different memory objects at subtraction, but does not check if the
+array index is correct. Furthermore, only cases are reported where
+stack-allocated objects are involved (no warnings on pointers to memory
+allocated by `malloc`).
+
+.. code-block:: c
+
+ void test() {
+   int a, b, c[10], d[10];
+   int x = &c[3] - &c[1];
+   x = &d[4] - &c[1]; // warn: 'c' and 'd' are different arrays
+   x = (&a + 1) - &a;
+   x = &b - &a; // warn: 'a' and 'b' are different variables
+ }
+
+ struct S {
+   int x[10];
+   int y[10];
+ };
+
+ void test1() {
+   struct S a[10];
+   struct S b;
+   int d = &a[4] - &a[6];
+   d = &a[0].x[3] - &a[0].x[1];
+   d = a[0].y - a[0].x; // warn: 'S.b' and 'S.a' are different objects
+   d = (char *)&b.y - (char *)&b.x; // warn: different members of the same object
+   d = (char *)&b.y - (char *)&b; // warn: object of type S is not the same array as a member of it
+ }
+
+There may be existing applications that use code like above for calculating
+offsets of members in a structure, using pointer subtractions. This is still
+undefined behavior according to the standard and code like this can be replaced
+with the `offsetof` macro.
+
 .. _core-StackAddressEscape:
 
 core.StackAddressEscape (C)
@@ -2526,49 +2569,6 @@ Check for pointer arithmetic on locations other than array elements.
    p = &x + 1; // warn
  }
 
-.. _alpha-core-PointerSub:
-
-alpha.core.PointerSub (C)
-"""""""""""""""""""""""""
-Check for pointer subtractions on two pointers pointing to different memory
-chunks. According to the C standard §6.5.6 only subtraction of pointers that
-point into (or one past the end) the same array object is valid (for this
-purpose non-array variables are like arrays of size 1). This checker only
-searches for different memory objects at subtraction, but does not check if the
-array index is correct. Furthermore, only cases are reported where
-stack-allocated objects are involved (no warnings on pointers to memory
-allocated by `malloc`).
-
-.. code-block:: c
-
- void test() {
-   int a, b, c[10], d[10];
-   int x = &c[3] - &c[1];
-   x = &d[4] - &c[1]; // warn: 'c' and 'd' are different arrays
-   x = (&a + 1) - &a;
-   x = &b - &a; // warn: 'a' and 'b' are different variables
- }
-
- struct S {
-   int x[10];
-   int y[10];
- };
-
- void test1() {
-   struct S a[10];
-   struct S b;
-   int d = &a[4] - &a[6];
-   d = &a[0].x[3] - &a[0].x[1];
-   d = a[0].y - a[0].x; // warn: 'S.b' and 'S.a' are different objects
-   d = (char *)&b.y - (char *)&b.x; // warn: different members of the same object
-   d = (char *)&b.y - (char *)&b; // warn: object of type S is not the same array as a member of it
- }
-
-There may be existing applications that use code like above for calculating
-offsets of members in a structure, using pointer subtractions. This is still
-undefined behavior according to the standard and code like this can be replaced
-with the `offsetof` macro.
-
 .. _alpha-core-StackAddressAsyncEscape:
 
 alpha.core.StackAddressAsyncEscape (C)
diff --git a/clang/include/clang/StaticAnalyzer/Checkers/Checkers.td b/clang/include/clang/StaticAnalyzer/Checkers/Checkers.td
index 585246547b3dce..f4167b18b4879a 100644
--- a/clang/include/clang/StaticAnalyzer/Checkers/Checkers.td
+++ b/clang/include/clang/StaticAnalyzer/Checkers/Checkers.td
@@ -257,6 +257,11 @@ def NonnullGlobalConstantsChecker: Checker<"NonnilStringConstants">,
   Documentation<NotDocumented>,
   Hidden;
 
+def PointerSubChecker : Checker<"PointerSub">,
+  HelpText<"Check for pointer subtractions on two pointers pointing to "
+           "different memory chunks">,
+  Documentation<HasDocumentation>;
+
 } // end "core"
 
 let ParentPackage = CoreAlpha in {
@@ -291,11 +296,6 @@ def PointerArithChecker : Checker<"PointerArithm">,
            "elements">,
   Documentation<HasDocumentation>;
 
-def PointerSubChecker : Checker<"PointerSub">,
-  HelpText<"Check for pointer subtractions on two pointers pointing to "
-           "different memory chunks">,
-  Documentation<HasDocumentation>;
-
 def TestAfterDivZeroChecker : Checker<"TestAfterDivZero">,
   HelpText<"Check for division by variable that is later compared against 0. "
            "Either the comparison is useless or there is division by zero.">,
diff --git a/clang/test/Analysis/analyzer-enabled-checkers.c b/clang/test/Analysis/analyzer-enabled-checkers.c
index e605c62a66ad0e..db0c2f8366e38c 100644
--- a/clang/test/Analysis/analyzer-enabled-checkers.c
+++ b/clang/test/Analysis/analyzer-enabled-checkers.c
@@ -19,6 +19,7 @@
 // CHECK-NEXT: core.NonNullParamChecker
 // CHECK-NEXT: core.NonnilStringConstants
 // CHECK-NEXT: core.NullDereference
+// CHECK-NEXT: core.PointerSub
 // CHECK-NEXT: core.StackAddrEscapeBase
 // CHECK-NEXT: core.StackAddressEscape
 // CHECK-NEXT: core.UndefinedBinaryOperatorResult
diff --git a/clang/test/Analysis/pointer-sub-notes.c b/clang/test/Analysis/pointer-sub-notes.c
index 59681b4e7555af..95653fb352dbd9 100644
--- a/clang/test/Analysis/pointer-sub-notes.c
+++ b/clang/test/Analysis/pointer-sub-notes.c
@@ -1,4 +1,4 @@
-// RUN: %clang_analyze_cc1 -analyzer-checker=alpha.core.PointerSub -analyzer-output=text -verify %s
+// RUN: %clang_analyze_cc1 -analyzer-checker=core.PointerSub -analyzer-output=text -verify %s
 
 void different_1() {
   int a[3]; // expected-note{{Array at the left-hand side of subtraction}}
diff --git a/clang/test/Analysis/pointer-sub.c b/clang/test/Analysis/pointer-sub.c
index cf9eac1abc2dcc..649a60f545e810 100644
--- a/clang/test/Analysis/pointer-sub.c
+++ b/clang/test/Analysis/pointer-sub.c
@@ -1,4 +1,4 @@
-// RUN: %clang_analyze_cc1 -analyzer-checker=core,alpha.core.PointerSub -analyzer-output=text-minimal -verify %s
+// RUN: %clang_analyze_cc1 -analyzer-checker=core -analyzer-output=text-minimal -verify %s
 
 void f1(void) {
   int x, y, z[10];
diff --git a/clang/test/Analysis/std-c-library-functions-arg-enabled-checkers.c b/clang/test/Analysis/std-c-library-functions-arg-enabled-checkers.c
index 345a4e8f44efd1..7cf20011ba81ca 100644
--- a/clang/test/Analysis/std-c-library-functions-arg-enabled-checkers.c
+++ b/clang/test/Analysis/std-c-library-functions-arg-enabled-checkers.c
@@ -27,6 +27,7 @@
 // CHECK-NEXT: core.NonNullParamChecker
 // CHECK-NEXT: core.NonnilStringConstants
 // CHECK-NEXT: core.NullDereference
+// CHECK-NEXT: core.PointerSub
 // CHECK-NEXT: core.StackAddrEscapeBase
 // CHECK-NEXT: core.StackAddressEscape
 // CHECK-NEXT: core.UndefinedBinaryOperatorResult

``````````

</details>


https://github.com/llvm/llvm-project/pull/107596


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