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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="#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>
</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><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></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><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></td>
<td><div class="exampleContainer expandable">
<div class="example"><pre>
void test() {
  BOOL b = -1; // warn
}
</pre></div></div></td></tr>


<tr><td><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></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><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></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><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></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><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></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><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></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><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></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><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></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><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></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><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></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><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></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><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></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><div class="namedescr expandable"><span class="name">
alpha.cplusplus.VirtualCall</span><span class="lang">
(C++)</span><div class="descr">
Check virtual member function calls during construction or 
destruction.</div></div></td>
<td><div class="exampleContainer expandable">
<div class="example"><pre>
class A {
public:
  A() { 
    f(); // warn
  }
  virtual void f();
};
</pre></div><div class="separator"></div>
<div class="example"><pre>
class A {
public:
  ~A() {
    this-&gt;f(); // warn
  }
  virtual void f();
};
</pre></div></div></td></tr>

<tbody>
<tr><td><div class="namedescr expandable"><span class="name">
alpha.cplusplus.UninitializedObject</span><span class="lang">
(C++)</span><div class="descr">
This checker reports uninitialized fields in objects created
after a constructor call. It doesn't only find direct uninitialized
fields, but rather makes a deep inspection of the object,
analyzing all of it's fields subfields. <br>
The checker regards inherited fields as direct fields, so one
will recieve warnings for uninitialized inherited data members
as well. <br>
<br>
It has several options:
<ul>
  <li>
    "<code>Pedantic</code>" (boolean). If its not set or is set to false, the checker
    won't emit warnings for objects that don't have at least one initialized
    field. This may be set with <br>
    <code>-analyzer-config alpha.cplusplus.UninitializedObject:Pedantic=true</code>.
  </li>
  <li>
    "<code>NotesAsWarnings</code>" (boolean). If set to true, the checker will emit a
    warning for each uninitalized field, as opposed to emitting one warning
    per constructor call, and listing the uninitialized fields that belongs
    to it in notes. Defaults to false. <br>
    <code>-analyzer-config alpha.cplusplus.UninitializedObject:NotesAsWarnings=true</code>.
  </li>
  <li>
    "<code>CheckPointeeInitialization</code>" (boolean). If set to false, the checker will
    not analyze the pointee of pointer/reference fields, and will only check
    whether the object itself is initialized. Defaults to false. <br>
    <code>-analyzer-config alpha.cplusplus.UninitializedObject:CheckPointeeInitialization=true</code>.
  </li>
  <li>
    "<code>IgnoreRecordsWithField</code>" (string). If supplied, the checker will not
     analyze structures that have a field with a name or type name that
     matches the given pattern. Defaults to <code>""</code>.

     <code>-analyzer-config alpha.cplusplus.UninitializedObject:IgnoreRecordsWithField="[Tt]ag|[Kk]ind"</code>.
  </li>
</ul></div></div></td>
<td><div class="exampleContainer expandable">
<div class="example"><pre>
// With Pedantic and CheckPointeeInitialization set to true

struct A {
  struct B {
    int x; // note: uninitialized field 'this->b.x'
           // note: uninitialized field 'this->bptr->x'
    int y; // note: uninitialized field 'this->b.y'
           // note: uninitialized field 'this->bptr->y'
  };
  int *iptr; // note: uninitialized pointer 'this->iptr'
  B b;
  B *bptr;
  char *cptr; // note: uninitialized pointee 'this->cptr'

  A (B *bptr, char *cptr) : bptr(bptr), cptr(cptr) {}
};

void f() {
  A::B b;
  char c;
  A a(&b, &c); // warning: 6 uninitialized fields
               //          after the constructor call
}
</pre></div><div class="separator"></div>
<div class="example"><pre>
// With Pedantic set to false and
// CheckPointeeInitialization set to true
// (every field is uninitialized)

struct A {
  struct B {
    int x;
    int y;
  };
  int *iptr;
  B b;
  B *bptr;
  char *cptr;

  A (B *bptr, char *cptr) : bptr(bptr), cptr(cptr) {}
};

void f() {
  A::B b;
  char c;
  A a(&b, &c); // no warning
}
</pre></div><div class="separator"></div>
<div class="example"><pre>
// With Pedantic and CheckPointeeInitialization set to false
// (pointees are regarded as initialized)

struct A {
  struct B {
    int x; // note: uninitialized field 'this->b.x'
    int y; // note: uninitialized field 'this->b.y'
  };
  int *iptr; // note: uninitialized pointer 'this->iptr'
  B b;
  B *bptr;
  char *cptr;

  A (B *bptr, char *cptr) : bptr(bptr), cptr(cptr) {}
};

void f() {
  A::B b;
  char c;
  A a(&b, &c); // warning: 3 uninitialized fields
               //          after the constructor call
}
<div class="example"><pre>


</pre></div></div></td></tr>

</tbody></table>


<!-- =============================== va_list =============================== -->
<h3 id="valist_alpha_checkers">Variable Argument 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><div class="namedescr expandable"><span class="name">
alpha.valist.CopyToSelf</span><span class="lang">
(C)</span><div class="descr">
Calls to the <code>va_copy</code> macro should not copy onto itself.</div></div></td>
<td><div class="exampleContainer expandable">
<div class="example"><pre>
#include &lt;stdarg.h&gt;

void test(int x, ...) {
  va_list args;
  va_start(args, x);
  va_copy(args, args); // warn
  va_end(args);
}
</pre></div></div></td></tr>

<tr><td><div class="namedescr expandable"><span class="name">
alpha.valist.Uninitialized</span><span class="lang">
(C)</span><div class="descr">
Calls to the <code>va_arg</code>, <code>va_copy</code>, or
<code>va_end</code> macro must happen after calling <code>va_start</code> and
before calling <code>va_end</code>.</div></div></td>
<td><div class="exampleContainer expandable">
<div class="example"><pre>
#include &lt;stdarg.h&gt;

void test(int x, ...) {
  va_list args;
  int y = va_arg(args, int); // warn
}
</pre></div>
<div class="example"><pre>
#include &lt;stdarg.h&gt;

void test(int x, ...) {
  va_list args;
  va_start(args, x);
  va_end(args);
  int z = va_arg(args, int); // warn
}
</pre></div></div></td></tr>

<tr><td><div class="namedescr expandable"><span class="name">
alpha.valist.Unterminated</span><span class="lang">
(C)</span><div class="descr">
Every <code>va_start</code> must be matched by a <code>va_end</code>. A va_list
can only be ended once.</div></div></td>
<td><div class="exampleContainer expandable">
<div class="example"><pre>
#include &lt;stdarg.h&gt;

void test(int x, ...) {
  va_list args;
  va_start(args, x);
  int y = x + va_arg(args, int);
} // warn: missing va_end
</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><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></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>

<!-- ============================== 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><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></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><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></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><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></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><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></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><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></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><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></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><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></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><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></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><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></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><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></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><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></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><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></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><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="http://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="http://llvm.org/devmtg/2012-11/">
2012 LLVM Developers' Meeting).</a></div></div></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><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></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><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></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><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></td></tr>


<tr><td><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></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>

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