Clang

https://releases.llvm.org/13.0.0/tools/clang/docs/
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### Example header B.h includes A.h

Source: https://releases.llvm.org/13.0.0/tools/clang/docs/Modules.html

Header file B.h includes A.h. Part of the prebuilt modules example setup.

```c
/* B.h */
#include "A.h"

```

--------------------------------

### caseStmt example

Source: https://releases.llvm.org/13.0.0/tools/clang/docs/LibASTMatchersReference.html

Example for the caseStmt matcher.

```cpp
  switch(a) { case 42: break; default: break; }
```

--------------------------------

### forEachConstructorInitializer example

Source: https://releases.llvm.org/13.0.0/tools/clang/docs/LibASTMatchersReference.html

Example for forEachConstructorInitializer matcher, binding each field initializer.

```cpp
class A { A() : i(42), j(42) {} int i; int j; };
cxxConstructorDecl(forEachConstructorInitializer(
  forField(decl().bind("x"))
))
```

--------------------------------

### continueStmt example

Source: https://releases.llvm.org/13.0.0/tools/clang/docs/LibASTMatchersReference.html

Example for the continueStmt matcher.

```cpp
  while (true) { continue; }
```

--------------------------------

### cStyleCastExpr example

Source: https://releases.llvm.org/13.0.0/tools/clang/docs/LibASTMatchersReference.html

Example for the cStyleCastExpr matcher.

```cpp
  int i = (int) 2.2f;
```

--------------------------------

### hasAnyConstructorInitializer example

Source: https://releases.llvm.org/13.0.0/tools/clang/docs/LibASTMatchersReference.html

Example for hasAnyConstructorInitializer matcher, matching a constructor initializer.

```cpp
struct Foo {
  Foo() : foo_(1) { }
  int foo_;
};
cxxRecordDecl(has(cxxConstructorDecl(
  hasAnyConstructorInitializer(anything())
)))
```

--------------------------------

### Example source file use.c

Source: https://releases.llvm.org/13.0.0/tools/clang/docs/Modules.html

Source file use.c includes B.h and calls a() if ENABLE_A is defined. Used in the prebuilt modules examples.

```c
/* use.c */
#include "B.h"
void use() {
#ifdef ENABLE_A
  a();
#endif
}

```

--------------------------------

### Getting Started: BankAccount class with GUARDED_BY

Source: https://releases.llvm.org/13.0.0/tools/clang/docs/ThreadSafetyAnalysis.html

Shows a minimal C++ class using the Thread Safety Analysis annotations. The example declares a Mutex member and a balance field guarded by it; the depositImpl method triggers a warning because it writes balance without locking mu. Use this as the starting point for annotating your own classes.

```cpp
#include "mutex.h"

class BankAccount {
private:
  Mutex mu;
  int   balance GUARDED_BY(mu);

  void depositImpl(int amount) {
    balance += amount;       // WARNING! Cannot write balance without locking mu.
  }
};
```

--------------------------------

### ForEachMacros configuration example

Source: https://releases.llvm.org/13.0.0/tools/clang/docs/ClangFormatStyleOptions.html

Shows how to configure ForEachMacros in the .clang-format configuration file.

```yaml
ForEachMacros: ['RANGES_FOR', 'FOREACH']

```

--------------------------------

### cxxDeductionGuideDecl matcher example

Source: https://releases.llvm.org/13.0.0/tools/clang/docs/LibASTMatchersReference.html

Example for cxxDeductionGuideDecl matcher. It matches the deduction guide 'X(int) -> X<int>'.

```cpp
Matches user-defined and implicitly generated deduction guide.

Example matches the deduction guide.
  template<typename T>
  class X { X(int) };
  X(int) -> X<int>;
```

--------------------------------

### Compile and run commands for trace-pc-guard example

Source: https://releases.llvm.org/13.0.0/tools/clang/docs/SanitizerCoverage.html

Compile the example with -fsanitize-coverage=trace-pc-guard, link with the callback object and AddressSanitizer, then run with ASAN_OPTIONS to strip the path prefix.

```bash
clang++ -g  -fsanitize-coverage=trace-pc-guard trace-pc-guard-example.cc -c
clang++ trace-pc-guard-cb.cc trace-pc-guard-example.o -fsanitize=address
ASAN_OPTIONS=strip_path_prefix=`pwd`/ ./a.out

```

--------------------------------

### BreakBeforeBraces GNU example

Source: https://releases.llvm.org/13.0.0/tools/clang/docs/ClangFormatStyleOptions.html

Example for the BreakBeforeBraces style option with configuration value GNU. Braces are always broken and control statements get an extra indentation level.

```cpp
namespace N
{
enum E
{
  E1,
  E2,
};

class C
{
public:
  C();
};

bool baz(int i)
{
  try
    {
      do
        {
          switch (i)
            {
            case 1:
              {
                foobar();
                break;
              }
            default:
              {
                break;
              }
            }
        }
      while (--i);
      return true;
    }
  catch (...)
    {
      handleError();
      return false;
    }
}

void foo(bool b)
{
  if (b)
    {
      baz(2);
    }
  else
    {
      baz(5);
    }
}

void bar() { foo(true); }
} // namespace N

```

--------------------------------

### Export-as example

Source: https://releases.llvm.org/13.0.0/tools/clang/docs/Modules.html

Example showing that MyFrameworkCore is re-exported via the module MyFramework.

```plaintext
module MyFrameworkCore {
  export_as MyFramework
}

```

--------------------------------

### isExplicit matcher example

Source: https://releases.llvm.org/13.0.0/tools/clang/docs/LibASTMatchersReference.html

Example for the isExplicit matcher. Shows a template struct with constructors, conversion functions, and deduction guides, some marked explicit. The matcher matches only those with explicit specifier resolved to true.

```cpp
template<bool b>
  struct S {
    S(int); // #1
    explicit S(double); // #2
    operator int(); // #3
    explicit operator bool(); // #4
    explicit(false) S(bool) // # 7
    explicit(true) S(char) // # 8
    explicit(b) S(S) // # 9
  };
  S(int) -> S<true> // #5
  explicit S(double) -> S<false> // #6
```

--------------------------------

### Generated aarch64 assembly with -O2

Source: https://releases.llvm.org/13.0.0/tools/clang/docs/ShadowCallStack.html

Output of compiling the example with -O2. Shows the stack frame setup and call to bar.

```assembly
stp     x29, x30, [sp, #-16]!
mov     x29, sp
bl      bar
add     w0, w0, #1
ldp     x29, x30, [sp], #16
ret

```

--------------------------------

### Install Ninja binary to /usr/local/bin

Source: https://releases.llvm.org/13.0.0/tools/clang/docs/HowToSetupToolingForLLVM.html

Copies the built Ninja binary to /usr/local/bin and makes it executable. Ninja does not require installation and can be placed anywhere in $PATH.

```shell
$ sudo cp ninja /usr/local/bin/
$ sudo chmod a+rx /usr/local/bin/ninja

```

--------------------------------

### ShortNamespaceLines comparison example

Source: https://releases.llvm.org/13.0.0/tools/clang/docs/ClangFormatStyleOptions.html

Shows how ShortNamespaceLines affects whether FixNamespaceComments adds end comments. With a value of 1, short namespaces (like namespace a) do not get an end comment; with 0, they do. Longer namespaces (like namespace b) always get the comment.

```cpp
ShortNamespaceLines: 1     vs.     ShortNamespaceLines: 0
namespace a {                      namespace a {
  int foo;                           int foo;
}                                  } // namespace a

ShortNamespaceLines: 1     vs.     ShortNamespaceLines: 0
namespace b {                      namespace b {
  int foo;                           int foo;
  int bar;                           int bar;
} // namespace b                   } // namespace b

```

--------------------------------

### isVirtual examples

Source: https://releases.llvm.org/13.0.0/tools/clang/docs/LibASTMatchersReference.html

Two examples for isVirtual: one showing a virtual method and one showing virtual inheritance, with the matcher matching the virtual method and the virtual base classes.

```cpp
class A {
 public:
  virtual void x(); // matches x
};
```

```cpp
class Base {};
class DirectlyDerived : virtual Base {}; // matches Base
class IndirectlyDerived : DirectlyDerived, Base {}; // matches Base
```

--------------------------------

### Example output with -fdiagnostics-print-source-range-info

Source: https://releases.llvm.org/13.0.0/tools/clang/docs/UsersManual.html

Shows the machine-parseable source range information printed after the file/line/column. The ranges are brace-enclosed and list start and end locations. Column numbers count bytes from the beginning of the line.

```text
exprs.c:47:15:{47:8-47:14}{47:17-47:24}: error: invalid operands to binary expression ('int *' and '_Complex float')
   P = (P-42) + Gamma*4;
       ~~~~~~ ^ ~~~~~~~

```

--------------------------------

### Input for begin() replacement

Source: https://releases.llvm.org/13.0.0/tools/clang/docs/LibASTMatchersReference.html

Example input code with a const container and a range-based for loop.

```cpp
void foo() {
  const Container c;
  c.begin();

  for (auto i : c) {
  }
}
```

--------------------------------

### SpacesInLineCommentPrefix examples

Source: https://releases.llvm.org/13.0.0/tools/clang/docs/ClangFormatStyleOptions.html

Shows the effect of SpacesInLineCommentPrefix with different Minimum and Maximum values. Minimum = 1 Maximum = -1 forces one space but allows more; Minimum = 0 Maximum = 0 forces comments to start directly after the slashes.

```cpp
Minimum = 1 Maximum = -1 // One space is forced
// but more spaces are possible
Minimum = 0 Maximum = 0 //Forces to start every comment directly after the slashes

```

--------------------------------

### BraceWrapping: example configuration

Source: https://releases.llvm.org/13.0.0/tools/clang/docs/ClangFormatStyleOptions.html

Shows how to configure BraceWrapping when BreakBeforeBraces is set to Custom.

```yaml
# Example of usage:
BreakBeforeBraces: Custom
BraceWrapping:
  AfterEnum: true
  AfterStruct: false
  SplitEmptyFunction: false

```

--------------------------------

### Pointer dangling example with gsl::Owner and gsl::Pointer

Source: https://releases.llvm.org/13.0.0/tools/clang/docs/AttributeReference.html

Shows how the analysis treats a Pointer constructed from an Owner: the Pointer is considered to point inside the Owner, and becomes dangling when the Owner's lifetime ends. The final call to get() is an error.

```cpp
int f() {
  IntPointer P;
  if (true) {
    IntOwner O(7);
    P = IntPointer(O); // P "points into" O
  } // P is dangling
  return P.get(); // error: Using a dangling Pointer.
}

```

--------------------------------

### Enable all extensions except double support on R600 using -cl-ext

Source: https://releases.llvm.org/13.0.0/tools/clang/docs/OpenCLSupport.html

Use -cl-ext=-all,+cl_khr_fp16 to enable all known extensions except double support, while explicitly enabling the fp16 extension for the R600 target.

```bash
$ clang -cc1 -triple r600-unknown-unknown -cl-ext=-all,+cl_khr_fp16 test.cl
```

--------------------------------

### hasExternalFormalLinkage examples

Source: https://releases.llvm.org/13.0.0/tools/clang/docs/LibASTMatchersReference.html

Shows examples for hasExternalFormalLinkage. First example matches only z with varDecl(hasExternalFormalLinkage()). Second example matches f() because it has external formal linkage despite being unique to the translation unit.

```cpp
void f() {
  int x;
  static int y;
}
int z;
```

```cpp
namespace {
void f() {}
}
```

--------------------------------

### cxxDefaultArgExpr example

Source: https://releases.llvm.org/13.0.0/tools/clang/docs/LibASTMatchersReference.html

Example for the cxxDefaultArgExpr matcher.

```cpp
  void f(int x, int y = 0);
  f(42);
```

--------------------------------

### Example module.modulemap defining modules A and B

Source: https://releases.llvm.org/13.0.0/tools/clang/docs/Modules.html

Module map file defining modules A and B, with B exporting all its submodules. Used in the prebuilt modules examples.

```c
/* module.modulemap */
module A {
  header "A.h"
}
module B {
  header "B.h"
  export *
}

```

--------------------------------

### cxxConstructExpr example

Source: https://releases.llvm.org/13.0.0/tools/clang/docs/LibASTMatchersReference.html

Example for the cxxConstructExpr matcher.

```cpp
  void f(const string &a, const string &b);
  char *ptr;
  int n;
  f(string(ptr, n), ptr);
```

--------------------------------

### compile_flags.txt example

Source: https://releases.llvm.org/13.0.0/tools/clang/docs/JSONCompilationDatabase.html

Example of a compile_flags.txt file for simple projects. Each line is one argument; here -I and libwidget/include are separate lines because they are two arguments. Paths are relative to the directory containing the file.

```text
-xc++
-I
libwidget/include/

```

--------------------------------

### cxxConstCastExpr example

Source: https://releases.llvm.org/13.0.0/tools/clang/docs/LibASTMatchersReference.html

Example for the cxxConstCastExpr matcher.

```cpp
  int n = 42;
  const int &r(n);
  int* p = const_cast<int*>(&r);
```

--------------------------------

### cxxCatchStmt example

Source: https://releases.llvm.org/13.0.0/tools/clang/docs/LibASTMatchersReference.html

Example for the cxxCatchStmt matcher.

```cpp
  try {} catch(int i) {}
```

--------------------------------

### Run with UBSAN_OPTIONS=print_stacktrace=1

Source: https://releases.llvm.org/13.0.0/tools/clang/docs/UndefinedBehaviorSanitizer.html

Run your program with the environment variable `UBSAN_OPTIONS=print_stacktrace=1` to enable symbolized stack traces. Requires `llvm-symbolizer` in `PATH`.

```text
UBSAN_OPTIONS=print_stacktrace=1
```

--------------------------------

### Run with argument 'with-foo'

Source: https://releases.llvm.org/13.0.0/tools/clang/docs/SanitizerCoverage.html

Command to run the example with an argument, which triggers the call to foo().

```bash
ASAN_OPTIONS=strip_path_prefix=`pwd`/ ./a.out with-foo

```

--------------------------------

### cxxBoolLiteral example

Source: https://releases.llvm.org/13.0.0/tools/clang/docs/LibASTMatchersReference.html

Example for the cxxBoolLiteral matcher.

```cpp
  true
```

--------------------------------

### Example header A.h with conditional function

Source: https://releases.llvm.org/13.0.0/tools/clang/docs/Modules.html

Header file A.h defines function a() only when ENABLE_A is defined. Used in the prebuilt modules examples.

```c
/* A.h */
#ifdef ENABLE_A
void a() {}
#endif

```

--------------------------------

### cxxBindTemporaryExpr example

Source: https://releases.llvm.org/13.0.0/tools/clang/docs/LibASTMatchersReference.html

Example for the cxxBindTemporaryExpr matcher.

```cpp
  FunctionTakesString(GetStringByValue());
  FunctionTakesStringByPointer(GetStringPointer());
```

--------------------------------

### Output without arguments

Source: https://releases.llvm.org/13.0.0/tools/clang/docs/SanitizerCoverage.html

Output when running the example without arguments, showing initialization and guard hits in main.

```text
INIT: 0x71bcd0 0x71bce0
guard: 0x71bcd4 2 PC 0x4ecd5b in main trace-pc-guard-example.cc:2
guard: 0x71bcd8 3 PC 0x4ecd9e in main trace-pc-guard-example.cc:3:7

```

--------------------------------

### cudaKernelCallExpr example

Source: https://releases.llvm.org/13.0.0/tools/clang/docs/LibASTMatchersReference.html

Example for the cudaKernelCallExpr matcher.

```cpp
  kernel<<<i,j>>>();
```

--------------------------------

### coyieldExpr example

Source: https://releases.llvm.org/13.0.0/tools/clang/docs/LibASTMatchersReference.html

Example for the coyieldExpr matcher.

```cpp
  co_yield 1;
```

--------------------------------

### MacroBlockBegin and MacroBlockEnd example

Source: https://releases.llvm.org/13.0.0/tools/clang/docs/ClangFormatStyleOptions.html

Shows how to configure MacroBlockBegin and MacroBlockEnd to treat macros as block delimiters. The example demonstrates the difference with and without the configuration, affecting indentation of code inside macro blocks.

```cpp
# With:
MacroBlockBegin: "^NS_MAP_BEGIN|\
NS_TABLE_HEAD$"
MacroBlockEnd: "^\
NS_MAP_END|\
NS_TABLE_.*_END$"

NS_MAP_BEGIN
  foo();
NS_MAP_END

NS_TABLE_HEAD
  bar();
NS_TABLE_FOO_END

# Without:
NS_MAP_BEGIN
foo();
NS_MAP_END

NS_TABLE_HEAD
bar();
NS_TABLE_FOO_END

```

--------------------------------

### coreturnStmt example

Source: https://releases.llvm.org/13.0.0/tools/clang/docs/LibASTMatchersReference.html

Example for the coreturnStmt matcher.

```cpp
  while (true) { co_return; }
```
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