Files
carbon-lang/toolchain/driver/driver_fuzzer.cpp
Chandler Carruth 2c9739799b Render diagnostics through the terminal library (#7683)
Diagnostic rendering was part of the data model: `Loc::FormatLocation`
and
`Loc::FormatSnippet` wrote plain text to a stream, so no capability,
color, or
terminal width could reach them.

A diagnostic is now one message with labels, contexts, and location
information
attached, and `Diagnostics::Renderer` draws it into a
`Terminal::Buffer`. The
design is in `toolchain/docs/diagnostics_rendering.md` (#7668),
authoring in
`toolchain/docs/diagnostics.md`.

Before:

```
example.carbon:6:3: error: 1 argument passed to function expecting 0 arguments
  Run0(1);
  ^~~~~~~
example.carbon:3:1: note: calling function declared here
fn Run0() {}
^~~~~~~~~~~
```

After:

```
error: 1 argument passed to function expecting 0 arguments
       ╭─┤ example.carbon:6:3
       ┆
     3 │ fn Run0() {}
       · ─────┬─────
       ·      ╰──┤ calling function declared here
       ┆
->   6 │   Run0(1);
       ·   ───────
       ╰────────────
```

`--no-diagnostic-snippets` gives a compact form, `example.carbon:6:3-9`.
File
tests use it; the rendering tests under `toolchain/diagnostics/testdata`
ask for
snippets.

C++ interop diagnostics are data now rather than text Clang drew:
`SemIR::ClangSourceLocId` names a `clang::SourceRange`, and a Clang
location is
marked as the point it names.

`StreamConsumer` moves to a `:renderer` target that `:emitter` does not
depend
on, keeping `common/terminal` out of `consumer.h`. Capabilities come
from the
file behind the error stream, so tests get plain ASCII.

`renderer_fuzzer` draws diagnostics built from fuzzer bytes with every
capability combination, since a shape the renderer doesn't expect must
never be
why the compiler dies while reporting a problem.

TODOs mark the follow-ups: line weights and crossing lines, wrapping
that keeps
a quoted type whole, and ordering diagnostics that share a byte offset.

Also: `IncorrectExtension`'s hint moves into its message, since its note
had no
location of its own, and `strip_noise` in `check_diagnostics.py` blanks
multi-line `#define`s instead of deleting them.

Assisted-by: Claude Code
2026-10-15 06:08:57 +00:00

97 lines
3.1 KiB
C++

// Part of the Carbon Language project, under the Apache License v2.0 with LLVM
// Exceptions. See /LICENSE for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
#include <cstring>
#include <string>
#include "common/exe_path.h"
#include "common/raw_string_ostream.h"
#include "llvm/ADT/SmallVector.h"
#include "llvm/ADT/StringRef.h"
#include "llvm/Support/raw_ostream.h"
#include "testing/fuzzing/libfuzzer.h"
#include "toolchain/base/install_paths.h"
#include "toolchain/driver/driver.h"
namespace Carbon::Testing {
static const InstallPaths* install_paths = nullptr;
// NOLINTNEXTLINE(readability-non-const-parameter): External API required types.
extern "C" auto LLVMFuzzerInitialize(int* argc, char*** argv) -> int {
CARBON_CHECK(*argc >= 1, "Need the `argv[0]` value to initialize!");
install_paths = new InstallPaths(
InstallPaths::MakeForBazelRunfiles(FindExecutablePath((*argv)[0])));
return 0;
}
static auto Read(const unsigned char*& data, size_t& size, int& output)
-> bool {
if (size < sizeof(output)) {
return false;
}
std::memcpy(&output, data, sizeof(output));
size -= sizeof(output);
data += sizeof(output);
return true;
}
extern "C" auto LLVMFuzzerTestOneInput(const unsigned char* data, size_t size)
-> int {
// First use the data to compute the number of arguments. Note that for
// scaling reasons we don't allow 2^31 arguments, even empty ones. Simply
// creating the vector of those won't work. We limit this to 2^20 arguments
// total.
int num_args;
if (!Read(data, size, num_args) || num_args < 0 || num_args > (1 << 20)) {
return 0;
}
// Now use the data to compute the length of each argument. We don't want to
// exhaust all memory, so bound the search space to using 2^17 bytes of
// memory for the argument text itself.
size_t arg_length_sum = 0;
llvm::SmallVector<int> arg_lengths(num_args);
for (int& arg_length : arg_lengths) {
if (!Read(data, size, arg_length) || arg_length < 0) {
return 0;
}
arg_length_sum += arg_length;
if (arg_length_sum > (1 << 17)) {
return 0;
}
}
// Ensure we have enough data for all the arguments.
if (size < arg_length_sum) {
return 0;
}
// Lastly, read the contents of each argument out of the data.
llvm::SmallVector<llvm::StringRef> args;
args.reserve(num_args);
for (int arg_length : arg_lengths) {
args.push_back(
llvm::StringRef(reinterpret_cast<const char*>(data), arg_length));
data += arg_length;
size -= arg_length;
}
llvm::IntrusiveRefCntPtr<llvm::vfs::InMemoryFileSystem> fs =
new llvm::vfs::InMemoryFileSystem;
RawStringOstream error_stream;
llvm::raw_null_ostream null_ostream;
Driver driver(fs, install_paths, /*input_stream=*/nullptr, &null_ostream,
&error_stream, /*error_file=*/{}, /*fuzzing=*/true);
if (!driver.RunCommand(args).success) {
auto str = error_stream.TakeStr();
if (llvm::StringRef(str).find("error:") == llvm::StringRef::npos) {
llvm::errs() << "No error message on a failure!\n";
return 1;
}
}
return 0;
}
} // namespace Carbon::Testing