Merge #18009: tests: Add fuzzing harness for strprintf(…)

cc668d06fb71463fd406df761b0e89e25d4de968 tests: Add fuzzing harness for strprintf(...) (practicalswift)
ccc3c76e2b5d28a2372ae5752c08256396bf43e6 tests: Add fuzzer strprintf to FUZZERS_MISSING_CORPORA (temporarily) (practicalswift)
6ef04912af7f216f3112e0e9919f67e36415a792 tests: Update FuzzedDataProvider.h from upstream (LLVM) (practicalswift)

Pull request description:

  Add fuzzing harness for `strprintf(…)`.

  Update `FuzzedDataProvider.h`.

  Avoid hitting some issues in tinyformat (reported upstreams in https://github.com/c42f/tinyformat/issues/70).

  ---

  Found issues in tinyformat:

  **Issue 1.** The following causes a signed integer overflow followed by an allocation of 9 GB of RAM (or an OOM in memory constrained environments):

  ```
  strprintf("%.777777700000000$", 1.0);
  ```

  **Issue 2.** The following causes a stack overflow:

  ```
  strprintf("%987654321000000:", 1);
  ```

  **Issue 3.** The following causes a stack overflow:

  ```
  strprintf("%1$*1$*", -11111111);
  ```

  **Issue 4.** The following causes a `NULL` pointer dereference:

  ```
  strprintf("%.1s", (char *)nullptr);
  ```

  **Issue 5.** The following causes a float cast overflow:

  ```
  strprintf("%c", -1000.0);
  ```

  **Issue 6.** The following causes a float cast overflow followed by an invalid integer negation:

  ```
  strprintf("%*", std::numeric_limits<double>::lowest());
  ```

Top commit has no ACKs.

Tree-SHA512: 9b765559281470f4983eb5aeca94bab1b15ec9837c0ee01a20f4348e9335e4ee4e4fecbd7a1a5a8ac96aabe0f9eeb597b8fc9a2c8faf1bab386e8225d5cdbc18

0 files changed, 0 insertions, 0 deletions