Code:
  (lambda ()
    (c-ts-mode)
    (setq-local indent-tabs-mode nil)
    (setq-local c-ts-mode-indent-offset 2)
    (c-ts-mode-set-style 'gnu)
    (indent-region (point-min) (point-max)))

Point-Char: |

Name: Basic

=-=
int
main (void)
{
  return 0;
}
=-=-=

Name: Hanging Braces (GNU Style)

=-=
int
main (void)
{
  if (true)
    {
    }
}
=-=-=

Name: Labels (GNU Style)

=-=
int
main (void)
{
 label:
  return 0;
  if (true)
    {
    label:
      return 0;
    }
  else
    {
      if (true)
        {
        label:
          return 0;
        }
    }
}
=-=-=

Name: For Loop with Multi-line Condition (GNU Style)

=-=
int main()
{
  for (int i = 0;
       i < b;
       i++)
    {
      return 0;
    }
}
=-=-=

Name: If-Else (GNU Style)

=-=
int main()
{
  if (true)
    {
      return 0;
    }
  else
    {
      return 1;
    }
}
=-=-=

Name: Consecutive blocks (GNU Style) (bug#60873)

=-=
int
main (int   argc,
      char *argv[])
{
  {
    int i = 0;
  }
}
=-=-=

Name: Bracket-less Block-Statement (GNU Style) (bug#61026)

=-=
int main() {
  while (true)
    if (true)
      {
        puts ("Hello");
      }
  for (int i=0;
       i<5;
       i++)
    if (true)
      {
        puts ("Hello");
      }
  do
    if (true)
      {
        puts ("Hello");
      }
  while (true);
  if (true)
    if (true)
      {
        puts ("Hello");
      }
}
=-=-=

Name: Multiline Parameter List (bug#60398)

=-=
int f2(int x,
       int y) {
  return x + y;
};
=-=-=

Name: Semi-colon in While Loop (bug#61291)

=-=
while (true)
  ;
for (int i = 0;
     i < 5;
     i++)
  ;
=-=-=

Name: Bracketless Simple Statement

=-=
for (int i = 0; i < 5; i++)
continue;

while (true)
return 1;

do
i++;
while (true)

if (true)
break;
else
break;
=-=
for (int i = 0; i < 5; i++)
  continue;

while (true)
  return 1;

do
  i++;
while (true)

if (true)
  break;
else
  break;
=-=-=

Name: Nested If-Else

=-=
if (true)
  return 0;
else if (false)
  return 1;
else if (true)
  return 2;
else if (false)
  return 3;
=-=-=

Name: Initializer List (Bug#61398)

=-=
int main()
{
  const char *emoticons[][2] =
    {
      {":-)", "SLIGHTLY SMILING FACE"},
      {";-)", "WINKING FACE"},
      {":-(", "SLIGHTLY FROWNING FACE"},
    };
}
=-=-=

Name: Return Compound Literal

=-=
struct pair { int fst, snd; };
struct pair
make_pair(int long_identifier_a[], int long_identifier_b[],
          int offset_a, int offset_b)
{
  int base_offset = 10;
  return (struct pair) { long_identifier_a[base_offset + offset_b],
                         long_identifier_b[base_offset + offset_b] };
}

=-=-=

Name: Switch-Case statement

=-=
int main() {
switch (a) {
case 1:
b = c;
return 10;
case 2:
{
a = b;
return 12
}
}
}
=-=
int main() {
  switch (a) {
  case 1:
    b = c;
    return 10;
  case 2:
    {
      a = b;
      return 12
    }
  }
}
=-=-=

Name: Multiline Block Comments 1 (bug#60270)

=-=
/**
 * @some_func:
 * @arg1:
 */
=-=-=

Name: Multiline Block Comments 2 (bug#60270)

=-=
/*
  some comment
 */
=-=-=

Name: Multiline Block Comments 3 (bug#60270)

=-=
/* some comment
 */
=-=-=

Name: Multiline Block Comments 4 (bug#60270)

=-=
/*
 * Some comment
 */
=-=-=

Name: Multiline Block Comments 5 (bug#60270)

=-=
/*
line one
line 2
 */
=-=
/*
  line one
  line 2
 */
=-=-=

Name: Block Comment prefixes (Bug#61314)

=-=-=
/*
- item1
- item2
- item3
*/
=-=-=
/*
  - item1
  - item2
  - item3
 */
=-=-=

Code:
  (lambda ()
    (c-ts-mode)
    (setq-local indent-tabs-mode nil)
    (setq-local c-ts-mode-indent-offset 8)
    (c-ts-mode-set-style 'linux)
    (indent-region (point-min) (point-max)))

Name: Labels (Linux Style)

=-=-=
int main (void)
{
label:
        return 0;
        if (true) {
label:
                return 0;
        }
        else {
                if (true) {
label:
                        return 0;
                }
        }
}
=-=-=

Name: Bracket-less Block-Statement (Linux Style) (bug#61026)

=-=
int main() {
  while (true)
    if (true) {
      puts ("Hello");
    }
  for (int i=0;
       i<5;
       i++)
    if (true) {
      puts ("Hello");
    }
  do
    if (true) {
      puts ("Hello");
    }
  while (true);
  if (true)
    if (true) {
      puts ("Hello");
    }
    else
      puts("Hello");
}
=-=-=

Name: Complicated mixed bracket matching indentation (bug#61142)

=-=
void foo(
         int foo) {
  for (;;)
    return 5;

  if (a == 0
      && b == 1
      && foo)
    {
      return 0;
    }
  else if (a == 1)
    {
      return 1;
    }
  else if (true)
    return 5;
  else
    {
      if (a == 0
          && b == 1
          && foo)
        for (
             int i = 0;
             i < 5;
             i++)
          if (true)
            do
              i = 5;
            while (true);
          else if (false)
            {
              return 6;
            }
          else
            if (true
                && false)
              return 6;
    }
}
=-=-=

Name: Block-Statement where first siblings are comments (Linux Style)

=-=
int main() {
  while (true) { /* foo */
    if (true) { // bar
      puts ("Hello");
    }
  }
  for (;;) {  // 1. fooo
    /* 2. baaa */
    /* 3. rrr */
    if (true)
      // 2. baaa
      puts ("Hello");
  }
  if (1) { // 1
    /*
     * 2
     */
    if (1) /*3*/ {
      /* 4 */
      puts("Hello");
    }
  }
}
=-=-=

Name: Initializer List (Linux Style) (Bug#61398)

=-=
int main()
{
  const char *emoticons[][2] = {
    {":-)", "SLIGHTLY SMILING FACE"},
    {";-)", "WINKING FACE"},
    {":-(", "SLIGHTLY FROWNING FACE"},
  };
}
=-=-=

Code:
  (lambda ()
    (c++-ts-mode)
    (setq-local indent-tabs-mode nil)
    (setq-local c-ts-mode-indent-offset 2)
    (indent-region (point-min) (point-max)))

Name: Declaration List (Namespace) (Bug#61635)

=-=
namespace test {
  class Name {
  };
}
=-=-=

Name: Namespace and template (bug#72263)

=-=
namespace A {

T myfunction1(const char *fname)
{
}

template <class T>
T myfunction2(const char *fname)
{
}
}
=-=
namespace A {

  T myfunction1(const char *fname)
  {
  }

  template <class T>
  T myfunction2(const char *fname)
  {
  }
}
=-=-=

Name: Return Aggregate Initialized Struct

=-=
struct pair { int x, y; }
pair
make_pair(int long_identifier_a[], int long_identifier_b[],
          int offset_a, int offset_b)
{
  int base_offset = 10;
  return { long_identifier_a[base_offset + offset_b],
       long_identifier_b[base_offset + offset_b] };
}
=-=
struct pair { int x, y; }
pair
make_pair(int long_identifier_a[], int long_identifier_b[],
          int offset_a, int offset_b)
{
  int base_offset = 10;
  return { long_identifier_a[base_offset + offset_b],
           long_identifier_b[base_offset + offset_b] };
}
=-=-=

Code:
  (lambda ()
    (c-ts-mode)
    (setq-local indent-tabs-mode nil)
    (setq-local c-ts-mode-indent-offset 2)
    (c-ts-mode-set-style 'gnu)
    (indent-for-tab-command))

Name: Empty Line
=-=
int main()
{
  |
}
=-=-=

Name: Empty Line Previous Sibling
=-=
int main()
{
  int a = 1;
  |
}
=-=-=

Name: Prev-Sibling But Not Trailing Comment

=-=
static int
required_matrix_height (struct window *w)
{
#ifdef HAVE_WINDOW_SYSTEM
  if (FRAME_WINDOW_P (f))
    {
      return 0;
    }
#endif /* Don't align to this comment.  */
  |
}
=-=-=

Name: Empty Line

=-=
int
main (void)
{
|
}
=-=
int
main (void)
{
  |
}
=-=-=

Name: Empty Line (Block Start)

=-=
int
main (void)
{
|
=-=
int
main (void)
{
  |
=-=-=

Code:
  (lambda ()
    (c-ts-mode)
    (setq-local indent-tabs-mode nil)
    (goto-line 3)
    (indent-for-tab-command))

Name: Block-Statement where previous sibling is comment

=-=
int main() {
    puts ("Hello"); // unusual indent and has trailing comment.
    return true; // Should align with previous non-comment sibling (rather than one level up against parent).
}
=-=-=