www/analyzer/alpha_checks.html

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<h1>Alpha Checkers</h1>
Experimental checkers in addition to the <a href = "available_checks.html">
Default Checkers</a>. These are checkers with known issues or limitations that
keep them from being on by default. They are likely to have false positives.
Bug reports are welcome but will likely not be investigated for some time.
Patches welcome!
<ul>
<li><a href="#clone_alpha_checkers">Clone Alpha Checkers</a></li>
<li><a href="#core_alpha_checkers">Core Alpha Checkers</a></li>
<li><a href="#cplusplus_alpha_checkers">C++ Alpha Checkers</a></li>
<li><a href="#llvm_alpha_checkers">LLVM Checkers</a></li>
<li><a href="#valist_alpha_checkers">Variable Argument Alpha Checkers</a></li>
<li><a href="#deadcode_alpha_checkers">Dead Code Alpha Checkers</a></li>
<li><a href="#osx_alpha_checkers">OS X Alpha Checkers</a></li>
<li><a href="#security_alpha_checkers">Security Alpha Checkers</a></li>
<li><a href="#unix_alpha_checkers">Unix Alpha Checkers</a></li>
<li><a href="#nondeterminism_alpha_checkers">Non-determinism Alpha Checkers</a></li>
</ul>

<!-- ============================= clone alpha ============================= -->

<h3 id="clone_alpha_checkers">Clone Alpha Checkers</h3>
<table class="checkers">
<colgroup><col class="namedescr"><col class="example"></colgroup>
<thead><tr><td>Name, Description</td><td>Example</td></tr></thead>

<tbody>
<tr><td><a id="alpha.clone.CloneChecker"><div class="namedescr expandable"><span class="name">
alpha.clone.CloneChecker</span><span class="lang">
(C, C++, ObjC)</span><div class="descr">
Reports similar pieces of code.</div></div></a></td>
<td><div class="exampleContainer expandable">
<div class="example"><pre>
void log();

int max(int a, int b) { // warn
  log();
  if (a > b)
    return a;
  return b;
}

int maxClone(int x, int y) { // similar code here
  log();
  if (x > y)
    return x;
  return y;
}
</pre></div></div></td></tr>
</tbody></table>

<!-- ============================= core alpha ============================= -->
<h3 id="core_alpha_checkers">Core Alpha Checkers</h3>
<table class="checkers">
<colgroup><col class="namedescr"><col class="example"></colgroup>
<thead><tr><td>Name, Description</td><td>Example</td></tr></thead>

<tbody>
<tr><td><a id="alpha.core.BoolAssignment"><div class="namedescr expandable"><span class="name">
alpha.core.BoolAssignment</span><span class="lang">
(ObjC)</span><div class="descr">
Warn about assigning non-{0,1} values to boolean variables.</div></div></a></td>
<td><div class="exampleContainer expandable">
<div class="example"><pre>
void test() {
  BOOL b = -1; // warn
}
</pre></div></div></td></tr>


<tr><td><a id="alpha.core.CallAndMessageUnInitRefArg"><div class="namedescr expandable"><span class="name">
alpha.core.CallAndMessageUnInitRefArg</span><span class="lang">
(C, C++)</span><div class="descr">
Check for uninitialized arguments in function calls and Objective-C
message expressions.</div></div></a></td>
<td><div class="exampleContainer expandable">
<div class="example"><pre>
void test(void) {
  int t;
  int &p = t;
  int &s = p;
  int &q = s;
  foo(q); // warn
}
</pre></div><div class="separator"></div>
<div class="example"><pre>
void test(void) {
  int x;
  foo(&x); // warn
}
</pre></div></div></td></tr>


<tr><td><a id="alpha.core.CastSize"><div class="namedescr expandable"><span class="name">
alpha.core.CastSize</span><span class="lang">
(C)</span><div class="descr">
Check when casting a malloc'ed type T, whether the size is a multiple of the
size of T (Works only with <span class="name">unix.Malloc</span>
or <span class="name">alpha.unix.MallocWithAnnotations</span>
checks enabled).</div></div></a></td>
<td><div class="exampleContainer expandable">
<div class="example"><pre>
void test() {
  int *x = (int *)malloc(11); // warn
}
</pre></div></div></td></tr>


<tr><td><a id="alpha.core.CastToStruct"><div class="namedescr expandable"><span class="name">
alpha.core.CastToStruct</span><span class="lang">
(C, C++)</span><div class="descr">
Check for cast from non-struct pointer to struct pointer.</div></div></a></td>
<td><div class="exampleContainer expandable">
<div class="example"><pre>
// C
struct s {};

void test(int *p) {
  struct s *ps = (struct s *) p; // warn
}
</pre></div><div class="separator"></div>
<div class="example"><pre>
// C++
class c {};

void test(int *p) {
  c *pc = (c *) p; // warn
}
</pre></div></div></td></tr>


<tr><td><a id="alpha.core.Conversion"><div class="namedescr expandable"><span class="name">
alpha.core.Conversion</span><span class="lang">
(C, C++, ObjC)</span><div class="descr">
Loss of sign or precision in implicit conversions</div></div></a></td>
<td><div class="exampleContainer expandable">
<div class="example"><pre>
void test(unsigned U, signed S) {
  if (S > 10) {
    if (U < S) {
    }
  }
  if (S < -10) {
    if (U < S) { // warn (loss of sign)
    }
  }
}
</pre></div><div class="separator"></div>
<div class="example"><pre>
void test() {
  long long A = 1LL << 60;
  short X = A; // warn (loss of precision)
}
</pre></div></div></td></tr>


<tr><td><a id="alpha.core.DynamicTypeChecker"><div class="namedescr expandable"><span class="name">
alpha.core.DynamicTypeChecker</span><span class="lang">
(ObjC)</span><div class="descr">
Check for cases where the dynamic and the static type of an
object are unrelated.</div></div></a></td>
<td><div class="exampleContainer expandable">
<div class="example"><pre>
id date = [NSDate date];

// Warning: Object has a dynamic type 'NSDate *' which is
// incompatible with static type 'NSNumber *'"
NSNumber *number = date;
[number doubleValue];
</pre></div></div></td></tr>


<tr><td><a id="alpha.core.FixedAddr"><div class="namedescr expandable"><span class="name">
alpha.core.FixedAddr</span><span class="lang">
(C)</span><div class="descr">
Check for assignment of a fixed address to a pointer.</div></div></a></td>
<td><div class="exampleContainer expandable">
<div class="example"><pre>
void test() {
  int *p;
  p = (int *) 0x10000; // warn
}
</pre></div></div></td></tr>


<tr><td><a id="alpha.core.IdenticalExpr"><div class="namedescr expandable"><span class="name">
alpha.core.IdenticalExpr</span><span class="lang">
(C, C++)</span><div class="descr">
Warn about suspicious uses of identical expressions.</div></div></a></td>
<td><div class="exampleContainer expandable">
<div class="example"><pre>
// C
void test() {
  int a = 5;
  int b = a | 4 | a; // warn: identical expr on both sides
}
</pre></div><div class="separator"></div>
<div class="example"><pre>
// C++
bool f(void);

void test(bool b) {
  int i = 10;
  if (f()) { // warn: true and false branches are identical
    do {
      i--;
    } while (f());
  } else {
    do {
      i--;
    } while (f());
  }
}
</pre></div></div></td></tr>


<tr><td><a id="alpha.core.PointerArithm"><div class="namedescr expandable"><span class="name">
alpha.core.PointerArithm</span><span class="lang">
(C)</span><div class="descr">
Check for pointer arithmetic on locations other than array
elements.</div></div></a></td>
<td><div class="exampleContainer expandable">
<div class="example"><pre>
void test() {
  int x;
  int *p;
  p = &amp;x + 1; // warn
}
</pre></div></div></td></tr>


<tr><td><a id="alpha.core.PointerSub"><div class="namedescr expandable"><span class="name">
alpha.core.PointerSub</span><span class="lang">
(C)</span><div class="descr">
Check for pointer subtractions on two pointers pointing to different memory
chunks.</div></div></a></td>
<td><div class="exampleContainer expandable">
<div class="example"><pre>
void test() {
  int x, y;
  int d = &amp;y - &amp;x; // warn
}
</pre></div></div></td></tr>


<tr><td><a id="alpha.core.SizeofPtr"><div class="namedescr expandable"><span class="name">
alpha.core.SizeofPtr</span><span class="lang">
(C)</span><div class="descr">
Warn about unintended use of <code>sizeof()</code> on pointer
expressions.</div></div></a></td>
<td><div class="exampleContainer expandable">
<div class="example"><pre>
struct s {};

int test(struct s *p) {
  return sizeof(p);
    // warn: sizeof(ptr) can produce an unexpected result
}
</pre></div></div></td></tr>


<tr><td><a id="alpha.core.StackAddressAsyncEscape"><div class="namedescr expandable"><span class="name">
alpha.core.StackAddressAsyncEscape</span><span class="lang">
(C)</span><div class="descr">
Check that addresses to stack memory do not escape the function that involves
<code>dispatch_after</code> or <code>dispatch_async</code>. This checker is
a part of core.StackAddressEscape, but is
<a href=https://reviews.llvm.org/D41042>temporarily disabled</a> until some
false positives are fixed.</div></div></a></td>
<td><div class="exampleContainer expandable">
<div class="example"><pre>
dispatch_block_t test_block_inside_block_async_leak() {
  int x = 123;
  void (^inner)(void) = ^void(void) {
    int y = x;
    ++y;
  };
  void (^outer)(void) = ^void(void) {
    int z = x;
    ++z;
    inner();
  };
  return outer; // warn: address of stack-allocated block is captured by a
                //       returned block
}
</pre></div></div></td></tr>


<tr><td><a id="alpha.core.TestAfterDivZero"><div class="namedescr expandable"><span class="name">
alpha.core.TestAfterDivZero</span><span class="lang">
(C, C++, ObjC)</span><div class="descr">
Check for division by variable that is later compared against 0.
Either the comparison is useless or there is division by zero.
</div></div></a></td>
<td><div class="exampleContainer expandable">
<div class="example"><pre>
void test(int x) {
  var = 77 / x;
  if (x == 0) { } // warn
}
</pre></div></div></td></tr>


</tbody></table>

<!-- =========================== cplusplus alpha =========================== -->
<h3 id="cplusplus_alpha_checkers">C++ Alpha Checkers</h3>
<table class="checkers">
<colgroup><col class="namedescr"><col class="example"></colgroup>
<thead><tr><td>Name, Description</td><td>Example</td></tr></thead>
<tbody>


<tr><td><a id="alpha.cplusplus.DeleteWithNonVirtualDtor"><div class="namedescr expandable"><span class="name">
alpha.cplusplus.DeleteWithNonVirtualDtor</span><span class="lang">
(C++)</span><div class="descr">
Reports destructions of polymorphic objects with a non-virtual destructor in
their base class
</div></div></a></td>
<td><div class="exampleContainer expandable">
<div class="example"><pre>
NonVirtual *create() {
  NonVirtual *x = new NVDerived(); // note: conversion from derived to base
                                   //       happened here
  return x;
}

void sink(NonVirtual *x) {
  delete x; // warn: destruction of a polymorphic object with no virtual
            //       destructor
}
</pre></div></div></td></tr>

<tr><td><a id="alpha.cplusplus.EnumCastOutOfRange"><div class="namedescr expandable"><span class="name">
alpha.cplusplus.EnumCastOutOfRange</span><span class="lang">
(C++)</span><div class="descr">
  Check for integer to enumeration casts that could result in undefined values.
</div></div></a></td>
  <td><div class="exampleContainer expandable">
    <div class="example"><pre>
enum TestEnum {
  A = 0
};

void foo() {
  TestEnum t = static_cast<TestEnum>(-1);
      // warn: the value provided to the cast expression is not in
               the valid range of values for the enum
}
</pre></div></div></td></tr>


<tr><td><a id="alpha.cplusplus.InvalidatedIterator"><div class="namedescr expandable"><span class="name">
alpha.cplusplus.InvalidatedIterator</span><span class="lang">
(C++)</span><div class="descr">
Check for use of invalidated iterators.
</div></div></a></td>
<td><div class="exampleContainer expandable">
<div class="example"><pre>
void bad_copy_assign_operator_list1(std::list<int> &L1,
                                    const std::list<int> &L2) {
  auto i0 = L1.cbegin();
  L1 = L2;
  *i0; // warn: invalidated iterator accessed
}
</pre></div></div></td></tr>


<tr><td><a id="alpha.cplusplus.IteratorRange"><div class="namedescr expandable"><span class="name">
alpha.cplusplus.IteratorRange</span><span class="lang">
(C++)</span><div class="descr">
Check for iterators used outside their valid ranges.
</div></div></a></td>
<td><div class="exampleContainer expandable">
<div class="example"><pre>
void simple_bad_end(const std::vector<int> &v) {
  auto i = v.end();
  *i; // warn: iterator accessed outside of its range
}
</pre></div></div></td></tr>


<tr><td><a id="alpha.cplusplus.MismatchedIterator"><div class="namedescr expandable"><span class="name">
alpha.cplusplus.MismatchedIterator</span><span class="lang">
(C++)</span><div class="descr">
Check for use of iterators of different containers where iterators of the same
container are expected.
</div></div></a></td>
<td><div class="exampleContainer expandable">
<div class="example"><pre>
void bad_insert3(std::vector<int> &v1, std::vector<int> &v2) {
  v2.insert(v1.cbegin(), v2.cbegin(), v2.cend()); // warn: container accessed
                                                  //       using foreign
                                                  //       iterator argument
  v1.insert(v1.cbegin(), v1.cbegin(), v2.cend()); // warn: iterators of
                                                  //       different containers
                                                  //       used where the same
                                                  //       container is
                                                  //       expected
  v1.insert(v1.cbegin(), v2.cbegin(), v1.cend()); // warn: iterators of
                                                  //       different containers
                                                  //       used where the same
                                                  //       container is
                                                  //       expected
}
</pre></div></div></td></tr>


<tr><td><a id="alpha.cplusplus.Move"><div class="namedescr expandable"><span class="name">
alpha.cplusplus.Move</span><span class="lang">
(C++)</span><div class="descr">
Method calls on a moved-from object and copying a moved-from object will be
reported.
</div></div></a></td>
<td><div class="exampleContainer expandable">
<div class="example"><pre>
struct A {
  void foo() {}
};

void f() {
  A a;
  A b = std::move(a); // note: 'a' became 'moved-from' here
  a.foo();            // warn: method call on a 'moved-from' object 'a'
}
</pre></div></div></td></tr>


</tbody></table>


<!-- =========================== dead code alpha =========================== -->
<h3 id="deadcode_alpha_checkers">Dead Code Alpha Checkers</h3>
<table class="checkers">
<colgroup><col class="namedescr"><col class="example"></colgroup>
<thead><tr><td>Name, Description</td><td>Example</td></tr></thead>

<tbody>
<tr><td><a id="alpha.deadcode.UnreachableCode"><div class="namedescr expandable"><span class="name">
alpha.deadcode.UnreachableCode</span><span class="lang">
(C, C++, ObjC)</span><div class="descr">
Check unreachable code.</div></div></a></td>
<td><div class="exampleContainer expandable">
<div class="example"><pre>
// C
int test() {
  int x = 1;
  while(x);
  return x; // warn
}
</pre></div><div class="separator"></div>
<div class="example"><pre>
// C++
void test() {
  int a = 2;

  while (a > 1)
    a--;

  if (a > 1)
    a++; // warn
}
</pre></div><div class="separator"></div>
<div class="example"><pre>
// Objective-C
void test(id x) {
  return;
  [x retain]; // warn
}
</pre></div></div></td></tr>
</tbody></table>

<!-- =========================== llvm alpha =========================== -->
<h3 id="llvm_alpha_checkers">LLVM Checkers</h3>
<table class="checkers">
<colgroup><col class="namedescr"><col class="example"></colgroup>
<thead><tr><td>Name, Description</td><td>Example</td></tr></thead>

<tbody>
<tr><td><a id="alpha.llvm.Conventions"><div class="namedescr expandable"><span class="name">
alpha.llvm.Conventions</span><span class="lang">
(C)</span><div class="descr">
Check code for LLVM codebase conventions:
<ul>
  <li>A <code>StringRef</code> should not be bound to a temporary std::string
  whose lifetime is shorter than the <code>StringRef</code>'s.</li>
  <li>Clang AST nodes should not have fields that can allocate memory.</li>
</ul>
</div></div></a></td>
<td><div class="exampleContainer expandable">
<div class="example"><pre>
<!-- TODO: Add examples, as currently it's hard to get this checker working. -->
</pre></div></div></td></tr>

</tbody></table>


<!-- ============================== OS X alpha ============================== -->
<h3 id="osx_alpha_checkers">OS X Alpha Checkers</h3>
<table class="checkers">
<colgroup><col class="namedescr"><col class="example"></colgroup>
<thead><tr><td>Name, Description</td><td>Example</td></tr></thead>

<tbody>
<tr><td><a id="alpha.osx.cocoa.DirectIvarAssignment"><div class="namedescr expandable"><span class="name">
alpha.osx.cocoa.DirectIvarAssignment</span><span class="lang">
(ObjC)</span><div class="descr">
Check that Objective C properties follow the following rule: the property
should be set with the setter, not though a direct assignment.</div></div></a></td>
<td><div class="exampleContainer expandable">
<div class="example"><pre>
@interface MyClass : NSObject {}
@property (readonly) id A;
- (void) foo;
@end

@implementation MyClass
- (void) foo {
  _A = 0; // warn
}
@end
</pre></div></div></td></tr>


<tr><td><a id="alpha.osx.cocoa.DirectIvarAssignmentForAnnotatedFunctions"><div class="namedescr expandable"><span class="name">
alpha.osx.cocoa.DirectIvarAssignmentForAnnotatedFunctions</span><span class="lang">
(ObjC)</span><div class="descr">
Check for direct assignments to instance variables in the methods annotated
with <code>objc_no_direct_instance_variable_assignment</code>.</div></div></a></td>
<td><div class="exampleContainer expandable">
<div class="example"><pre>
@interface MyClass : NSObject {}
@property (readonly) id A;
- (void) fAnnotated __attribute__((
    annotate("objc_no_direct_instance_variable_assignment")));
- (void) fNotAnnotated;
@end

@implementation MyClass
- (void) fAnnotated {
  _A = 0; // warn
}
- (void) fNotAnnotated {
  _A = 0; // no warn
}
@end
</pre></div></div></td></tr>


<tr><td><a id="alpha.osx.cocoa.InstanceVariableInvalidation"><div class="namedescr expandable"><span class="name">
alpha.osx.cocoa.InstanceVariableInvalidation</span><span class="lang">
(ObjC)</span><div class="descr">
Check that the invalidatable instance variables are invalidated in the methods
annotated with <code>objc_instance_variable_invalidator</code>.</div></div></a></td>
<td><div class="exampleContainer expandable">
<div class="example"><pre>
@protocol Invalidation &lt;NSObject&gt;
- (void) invalidate
  __attribute__((annotate("objc_instance_variable_invalidator")));
@end

@interface InvalidationImpObj : NSObject &lt;Invalidation&gt;
@end

@interface SubclassInvalidationImpObj : InvalidationImpObj {
  InvalidationImpObj *var;
}
- (void)invalidate;
@end

@implementation SubclassInvalidationImpObj
- (void) invalidate {}
@end
// warn: var needs to be invalidated or set to nil
</pre></div></div></td></tr>


<tr><td><a id="alpha.osx.cocoa.MissingInvalidationMethod"><div class="namedescr expandable"><span class="name">
alpha.osx.cocoa.MissingInvalidationMethod</span><span class="lang">
(ObjC)</span><div class="descr">
Check that the invalidation methods are present in classes that contain
invalidatable instance variables.</div></div></a></td>
<td><div class="exampleContainer expandable">
<div class="example"><pre>
@protocol Invalidation &lt;NSObject&gt;
- (void)invalidate
  __attribute__((annotate("objc_instance_variable_invalidator")));
@end

@interface NeedInvalidation : NSObject &lt;Invalidation&gt;
@end

@interface MissingInvalidationMethodDecl : NSObject {
  NeedInvalidation *Var; // warn
}
@end

@implementation MissingInvalidationMethodDecl
@end
</pre></div></div></td></tr>


<tr><td><a id="alpha.osx.cocoa.localizability.PluralMisuseChecker"><div class="namedescr expandable"><span class="name">
alpha.osx.cocoa.localizability.PluralMisuseChecker</span><span class="lang">
(ObjC)</span><div class="descr">
Warns against using one vs. many plural pattern in code
when generating localized strings.
</div></div></a></td>
<td><div class="exampleContainer expandable">
<div class="example"><pre>
NSString *reminderText =
  NSLocalizedString(@"None", @"Indicates no reminders");
if (reminderCount == 1) {
  // Warning: Plural cases are not supported across all languages.
  // Use a .stringsdict file instead
  reminderText =
    NSLocalizedString(@"1 Reminder", @"Indicates single reminder");
} else if (reminderCount >= 2) {
  // Warning: Plural cases are not supported across all languages.
  // Use a .stringsdict file instead
  reminderText =
    [NSString stringWithFormat:
      NSLocalizedString(@"%@ Reminders", @"Indicates multiple reminders"),
        reminderCount];
}
</pre></div></div></td></tr>

</tbody></table>

<!-- =========================== security alpha =========================== -->
<h3 id="security_alpha_checkers">Security Alpha Checkers</h3>
<table class="checkers">
<colgroup><col class="namedescr"><col class="example"></colgroup>
<thead><tr><td>Name, Description</td><td>Example</td></tr></thead>

<tbody>
<tr><td><a id="alpha.security.ArrayBound"><div class="namedescr expandable"><span class="name">
alpha.security.ArrayBound</span><span class="lang">
(C)</span><div class="descr">
Warn about buffer overflows (older checker).</div></div></a></td>
<td><div class="exampleContainer expandable">
<div class="example"><pre>
void test() {
  char *s = "";
  char c = s[1]; // warn
}
</pre></div><div class="separator"></div>
<div class="example"><pre>
struct seven_words {
  int c[7];
};

void test() {
  struct seven_words a, *p;
  p = &a;
  p[0] = a;
  p[1] = a;
  p[2] = a; // warn
}
</pre></div><div class="separator"></div>
<div class="example"><pre>
// note: requires unix.Malloc or
// alpha.unix.MallocWithAnnotations checks enabled.
void test() {
  int *p = malloc(12);
  p[3] = 4; // warn
}
</pre></div><div class="separator"></div>
<div class="example"><pre>
void test() {
  char a[2];
  int *b = (int*)a;
  b[1] = 3; // warn
}
</pre></div></div></td></tr>


<tr><td><a id="alpha.security.ArrayBoundV2"><div class="namedescr expandable"><span class="name">
alpha.security.ArrayBoundV2</span><span class="lang">
(C)</span><div class="descr">
Warn about buffer overflows (newer checker).</div></div></a></td>
<td><div class="exampleContainer expandable">
<div class="example"><pre>
void test() {
  char *s = "";
  char c = s[1]; // warn
}
</pre></div><div class="separator"></div>
<div class="example"><pre>
void test() {
  int buf[100];
  int *p = buf;
  p = p + 99;
  p[1] = 1; // warn
}
</pre></div><div class="separator"></div>
<div class="example"><pre>
// note: compiler has internal check for this.
// Use -Wno-array-bounds to suppress compiler warning.
void test() {
  int buf[100][100];
  buf[0][-1] = 1; // warn
}
</pre></div><div class="separator"></div>
<div class="example"><pre>
// note: requires alpha.security.taint check turned on.
void test() {
  char s[] = "abc";
  int x = getchar();
  char c = s[x]; // warn: index is tainted
}
</pre></div></div></td></tr>


<tr><td><a id="alpha.security.MallocOverflow"><div class="namedescr expandable"><span class="name">
alpha.security.MallocOverflow</span><span class="lang">
(C)</span><div class="descr">
Check for overflows in the arguments to <code>malloc()</code>.</div></div></a></td>
<td><div class="exampleContainer expandable">
<div class="example"><pre>
void test(int n) {
  void *p = malloc(n * sizeof(int)); // warn
}
</pre></div></div></td></tr>


<tr><td><a id="alpha.security.MmapWriteExec"><div class="namedescr expandable"><span class="name">
alpha.security.MmapWriteExec</span><span class="lang">
(C)</span><div class="descr">
Warn on <code>mmap()<code> calls that are both writable and executable.
</div></div></a></td>
<td><div class="exampleContainer expandable">
<div class="example"><pre>
void test(int n) {
  void *c = mmap(NULL, 32, PROT_READ | PROT_WRITE | PROT_EXEC,
                 MAP_PRIVATE | MAP_ANON, -1, 0);
  // warn: Both PROT_WRITE and PROT_EXEC flags are set. This can lead to
  //       exploitable memory regions, which could be overwritten with malicious
  //       code
}
</pre></div></div></td></tr>


<tr><td><a id="alpha.security.ReturnPtrRange"><div class="namedescr expandable"><span class="name">
alpha.security.ReturnPtrRange</span><span class="lang">
(C)</span><div class="descr">
Check for an out-of-bound pointer being returned to callers.</div></div></a></td>
<td><div class="exampleContainer expandable">
<div class="example"><pre>
static int A[10];

int *test() {
  int *p = A + 10;
  return p; // warn
}
</pre></div><div class="separator"></div>
<div class="example"><pre>
int test(void) {
  int x;
  return x; // warn: undefined or garbage returned
}
</pre></div></div></td></tr>


<tr><td><a id="alpha.security.taint.TaintPropagation"><div class="namedescr expandable"><span class="name">
alpha.security.taint.TaintPropagation</span><span class="lang">
(C)</span><div class="descr">
Generate taint information used by other checkers.</div></div></a></td>
<td><div class="exampleContainer expandable">
<div class="example"><pre>
void test() {
  char x = getchar(); // 'x' marked as tainted
  system(&x); // warn: untrusted data is passed to a system call
}
</pre></div><div class="separator"></div>
<div class="example"><pre>
// note: compiler internally checks if the second param to
// sprintf is a string literal or not.
// Use -Wno-format-security to suppress compiler warning.
void test() {
  char s[10], buf[10];
  fscanf(stdin, "%s", s); // 's' marked as tainted

  sprintf(buf, s); // warn: untrusted data as a format string
}
</pre></div><div class="separator"></div>
<div class="example"><pre>
void test() {
  size_t ts;
  scanf("%zd", &ts); // 'ts' marked as tainted
  int *p = (int *)malloc(ts * sizeof(int));
    // warn: untrusted data as buffer size
}
</pre></div></div></td></tr>

</tbody></table>

<!-- ============================= unix alpha ============================= -->
<h3 id="unix_alpha_checkers">Unix Alpha Checkers</h3>
<table class="checkers">
<colgroup><col class="namedescr"><col class="example"></colgroup>
<thead><tr><td>Name, Description</td><td>Example</td></tr></thead>
<tbody>


<tr><td><a id="alpha.unix.BlockInCriticalSection"><div class="namedescr expandable"><span class="name">
alpha.unix.BlockInCriticalSection</span><span class="lang">
(C)</span><div class="descr">
Check for calls to blocking functions inside a critical section. Applies to:
<div class=functions>
lock<br>
unlock<br>
sleep<br>
getc<br>
fgets<br>
read<br>
revc<br>
pthread_mutex_lock<br>
pthread_mutex_unlock<br>
mtx_lock<br>
mtx_timedlock<br>
mtx_trylock<br>
mtx_unlock<br>
lock_guard<br>
unique_lock</div>
</div></div></a></td>
<td><div class="exampleContainer expandable">
<div class="example"><pre>
void test() {
  std::mutex m;
  m.lock();
  sleep(3); // warn: a blocking function sleep is called inside a critical
            //       section
  m.unlock();
}
</pre></div></div></td></tr>


<tr><td><a id="alpha.unix.Chroot"><div class="namedescr expandable"><span class="name">
alpha.unix.Chroot</span><span class="lang">
(C)</span><div class="descr">
Check improper use of <code>chroot</code>.</div></div></a></td>
<td><div class="exampleContainer expandable">
<div class="example"><pre>
void f();

void test() {
  chroot("/usr/local");
  f(); // warn: no call of chdir("/") immediately after chroot
}
</pre></div></div></td></tr>


<tr><td><a id="alpha.unix.PthreadLock"><div class="namedescr expandable"><span class="name">
alpha.unix.PthreadLock</span><span class="lang">
(C)</span><div class="descr">
Simple lock -> unlock checker; applies to:<div class=functions>
pthread_mutex_lock<br>
pthread_rwlock_rdlock<br>
pthread_rwlock_wrlock<br>
lck_mtx_lock<br>
lck_rw_lock_exclusive<br>
lck_rw_lock_shared<br>
pthread_mutex_trylock<br>
pthread_rwlock_tryrdlock<br>
pthread_rwlock_tryrwlock<br>
lck_mtx_try_lock<br>
lck_rw_try_lock_exclusive<br>
lck_rw_try_lock_shared<br>
pthread_mutex_unlock<br>
pthread_rwlock_unlock<br>
lck_mtx_unlock<br>
lck_rw_done</div></div></div></a></td>
<td><div class="exampleContainer expandable">
<div class="example"><pre>
pthread_mutex_t mtx;

void test() {
  pthread_mutex_lock(&mtx);
  pthread_mutex_lock(&mtx);
    // warn: this lock has already been acquired
}
</pre></div><div class="separator"></div>
<div class="example"><pre>
lck_mtx_t lck1, lck2;

void test() {
  lck_mtx_lock(&lck1);
  lck_mtx_lock(&lck2);
  lck_mtx_unlock(&lck1);
    // warn: this was not the most recently acquired lock
}
</pre></div><div class="separator"></div>
<div class="example"><pre>
lck_mtx_t lck1, lck2;

void test() {
  if (lck_mtx_try_lock(&lck1) == 0)
    return;

  lck_mtx_lock(&lck2);
  lck_mtx_unlock(&lck1);
    // warn: this was not the most recently acquired lock
}
</pre></div></div></td></tr>


<tr><td><a id="alpha.unix.SimpleStream"><div class="namedescr expandable"><span class="name">
alpha.unix.SimpleStream</span><span class="lang">
(C)</span><div class="descr">
Check for misuses of stream APIs:<div class=functions>
fopen<br>
fclose</div>(demo checker, the subject of the demo
(<a href="https://llvm.org/devmtg/2012-11/Zaks-Rose-Checker24Hours.pdf">Slides</a>
,<a href="https://youtu.be/kdxlsP5QVPw">Video</a>)
by Anna Zaks and Jordan Rose presented at the <a href="https://llvm.org/devmtg/2012-11/">
2012 LLVM Developers' Meeting).</a></div></div></a></td>
<td><div class="exampleContainer expandable">
<div class="example"><pre>
void test() {
  FILE *F = fopen("myfile.txt", "w");
} // warn: opened file is never closed
</pre></div><div class="separator"></div>
<div class="example"><pre>
void test() {
  FILE *F = fopen("myfile.txt", "w");

  if (F)
    fclose(F);

  fclose(F); // warn: closing a previously closed file stream
}
</pre></div></div></td></tr>


<tr><td><a id="alpha.unix.Stream"><div class="namedescr expandable"><span class="name">
alpha.unix.Stream</span><span class="lang">
(C)</span><div class="descr">
Check stream handling functions:<div class=functions>fopen<br>
tmpfile<br>
fclose<br>
fread<br>
fwrite<br>
fseek<br>
ftell<br>
rewind<br>
fgetpos<br>
fsetpos<br>
clearerr<br>
feof<br>
ferror<br>
fileno</div></div></div></a></td>
<td><div class="exampleContainer expandable">
<div class="example"><pre>
void test() {
  FILE *p = fopen("foo", "r");
} // warn: opened file is never closed
</pre></div><div class="separator"></div>
<div class="example"><pre>
void test() {
  FILE *p = fopen("foo", "r");
  fseek(p, 1, SEEK_SET); // warn: stream pointer might be NULL
  fclose(p);
}
</pre></div><div class="separator"></div>
<div class="example"><pre>
void test() {
  FILE *p = fopen("foo", "r");

  if (p)
    fseek(p, 1, 3);
     // warn: third arg should be SEEK_SET, SEEK_END, or SEEK_CUR

  fclose(p);
}
</pre></div><div class="separator"></div>
<div class="example"><pre>
void test() {
  FILE *p = fopen("foo", "r");
  fclose(p);
  fclose(p); // warn: already closed
}
</pre></div><div class="separator"></div>
<div class="example"><pre>
void test() {
  FILE *p = tmpfile();
  ftell(p); // warn: stream pointer might be NULL
  fclose(p);
}
</pre></div></div></td></tr>


<tr><td><a id="alpha.unix.cstring.BufferOverlap"><div class="namedescr expandable"><span class="name">
alpha.unix.cstring.BufferOverlap</span><span class="lang">
(C)</span><div class="descr">
Checks for overlap in two buffer arguments; applies to:<div class=functions>
memcpy<br>
mempcpy</div></div></div></a></td>
<td><div class="exampleContainer expandable">
<div class="example"><pre>
void test() {
  int a[4] = {0};
  memcpy(a + 2, a + 1, 8); // warn
}
</pre></div></div></td></tr>


<tr><td><a id="alpha.unix.cstring.NotNullTerminated"><div class="namedescr expandable"><span class="name">
alpha.unix.cstring.NotNullTerminated</span><span class="lang">
(C)</span><div class="descr">
Check for arguments which are not null-terminated strings; applies
to:<div class=functions>
strlen<br>
strnlen<br>
strcpy<br>
strncpy<br>
strcat<br>
strncat</div></div></div></td>
<td><div class="exampleContainer expandable">
<div class="example"><pre>
void test() {
  int y = strlen((char *)&test); // warn
}
</pre></div></div></a></td></tr>


<tr><td><a id="alpha.unix.cstring.OutOfBounds"><div class="namedescr expandable"><span class="name">
alpha.unix.cstring.OutOfBounds</span><span class="lang">
(C)</span><div class="descr">
Check for out-of-bounds access in string functions; applies
to:<div class=functions>
strncopy<br>
strncat</div></div></div></a></td>
<td><div class="exampleContainer expandable">
<div class="example"><pre>
void test(char *y) {
  char x[4];
  if (strlen(y) == 4)
    strncpy(x, y, 5); // warn
}
</pre></div></div></td></tr>

</tbody></table>

<!-- =========================== nondeterminism alpha =========================== -->
<h3 id="nondeterminism_alpha_checkers">Non-determinism Alpha Checkers</h3>
<table class="checkers">
<colgroup><col class="namedescr"><col class="example"></colgroup>
<thead><tr><td>Name, Description</td><td>Example</td></tr></thead>

<tbody>
<tr><td><a id="alpha.nondeterminism.PointerIteration"><div class="namedescr expandable"><span class="name">
alpha.nondeterminism.PointerIteration</span><span class="lang">
(C++)</span><div class="descr">
Check for non-determinism caused by iterating unordered containers of pointers.</div></div></a></td>
<td><div class="exampleContainer expandable">
<div class="example"><pre>
// C++
void test() {
 int a = 1, b = 2;
 std::unordered_set<int *> UnorderedPtrSet = {&a, &b};

 for (auto i : UnorderedPtrSet) // warn
   f(i);
}
</pre></div></div></td></tr>
<tr><td><a id="alpha.nondeterminism.PointerSorting"><div class="namedescr expandable"><span class="name">
alpha.nondeterminism.PointerSorting</span><span class="lang">
(C++)</span><div class="descr">
Check for non-determinism caused by sorting of pointers.</div></div></a></td>
<td><div class="exampleContainer expandable">
<div class="example"><pre>
// C++
void test() {
 int a = 1, b = 2;
 std::vector<int *> V = {&a, &b};
 std::sort(V.begin(), V.end()); // warn
}
</pre></div></div></td></tr>
</tbody></table>

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