Diagnostics

A diagnostic library for printing compiler diagnostics.

Inspiration

• The diagnostic architecture is based on Google's Carbon Language diagnostic implementation, but not the exact implementation.
• CowString is inspired by Rust's Cow implementation.
• The error reporting or rendering on the terminal is closer to the Rust's.
• Stream has similar interface to llvm's raw_ostream with extensions.

Basic Concepts

1. Span

• Span is an absolute position inside the source string. This does not accept signed positions.
• LocRelSpan is a relative position that represent a subsection of the source that will be print by the diagnostic. It is similar to Span if the subsection is same as the whole source. This does not accept signed positions.
• MarkerRelSpan represent position relative to marker, which could be a negative offset.

Source: |xxxxxxxxxxxxxxx|xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx|xxxxxxxxxxx|
        ^		|		                        |
        |		|	    			        |
        Span		|xxxxxxxxxxxxxxxxxx^^^^^xxxxxxxxxxxxxxxx|
                        ^                  ^
                        |                  |
                        LocRelSpan         MarkerRelSpan

2. Context

This provides more information to the current diagnostic that will be rendered below the marked span.

Source: |xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx|
                                ^				^
                                |				|
                                |				This is an error
                                |- This is a second error.

3. Sub-Diagnostic

This helps the user to add multiple sub-diagnostics that is related to the current parent diagnostics; such as adding history or backtrace to the current diagnostic.

4. Token Diagnostic Location

This is a type of location that allows the user to pass individual tokens with custom styles (color and bold). It does not allow escape characters, and they'll be escaped.

5. Basic Diagnostic Location

This is a single string source that supports newlines and could be split into multiple lines or skipped if it has too many lines that don't have diagnostic.

6. Diagnostic Converter

This is a custom struct or class that inherits from the BasicDiagnosticConverter<LocT, DiagnosticKind>. It allows the user to customise or build diagnostic location to the diagnostic builder.

7. Consumer

This an object that consumes the diagnostics, which could a consumer that prints the diagnostics on the terminal or sorts the consumers. These consumers can be plugged into each other; such as plugging sort and stream consumers, which will sort first then print it on the terminal. There are three predefined consumers:

• BasicStreamDiagnosticConsumer<DiagnosticKind> This outputs the diagnostic to the Stream
• BasicErrorTrackingDiagnosticConsumer<DiagnosticKind> This tracks the error. If it encounters error, the error flag will be turned on.
• BasicSortingDiagnosticConsumer<DiagnosticKind> This sorts the diagnostics and needs a explicit flush.

8. Stream

This is an object that wraps standard out file descriptor, std::ostream, or llvm::raw_ostream (if DARK_LLVM_OS_STREAM is defined). This has almost similar interface to llvm's raw_ostream like change_color , reset_color, Color (enum)

#include <diagnostics.hpp>
int main() {
	dark::out().change_color(dark::Stream::RED) << "Hello";
	dark::out().change_color(dark::Stream::Color::GREEN, { .bold = true }) << " World";
	dark::out().reset_color();
}

9. Format String

This uses std::format under the hood. Therefore, any valid format string is a valid string. However, the user can specify data types that will be checked at compile-time. Valid type specifier:

• c for char
• s for string that could be both dynamic or static that will be stored inside the CowString
• u8, u16, u32, and u64
• i8, i16, i32, and i64
• f32 and f64
• no type indicates any

"This is {s} with {}" // valid
"This is {u32:<20} with {}" // valid
"This is {0} with {}" // invalid

How to use

This library is a C++ header only library so it very easy to use. You can clone the repo and add the include path to the include folder inside the cloned repo.

1. Clone the repo

git clone [email protected]:amitsingh19975/diagnostics.git

2. Include it in your project

# If you're using CMake
include_directories(repo_path/diagnostics/include)

# You could pass -I flag while compiling
cc -Irepo_path/diagnostics/include my_program

3. Including the header inside the C++ project

#include <diagnostics.hpp>
int main() {
    // ....
}

Usage

Defining Diagnostic Converter

#include <diagnostics.hpp>

enum class DiagnosticKind {
    InvalidFunctionDefinition,
    InvalidFunctionPrototype
};

/*
* 1. line number and column number are 1-based so if the user gives 0 then the location will not be printed.
*/
struct SimpleConverter: BasicDiagnosticConverter<unsigned, DiagnosticKind> {
    auto convert_loc(unsigned loc, [[maybe_unused]] builder_t builder) const -> dark::DiagnosticLocation override {
        return dark::DiagnosticLocation {
            .filename = "test.cpp",
            .source = dark::BasicDiagnosticLocationItem {
                .source = "void test( int a, int c );", // Subsection
                .line_number = 1, // Line where the marker starts.
                .column_number = loc + 1, // Column where the marker starts
                .source_location = 0, // This is an absolute position inside the original source.
                .length = 2 // Length of the diagnostic marker
            }
        };
    }
};

Using The Diagnostic Builder

int main() {
	auto consumer = dark::BasicStreamDiagnosticConsumer<DiagnosticKind>(dark::out());
    auto converter = SimpleConverter();
    auto emitter = dark::BasicDiagnosticEmitter(
        converter,
        consumer
    );

    static constexpr auto InvalidFunctionDefinition = dark_make_diagnostic_with_kind(
        DiagnosticKind::InvalidFunctionDefinition,
        "Invalid function definition for {s} at {u32}"
    );

    static constexpr auto InvalidFunctionPrototype = dark_make_diagnostic_with_kind(
        DiagnosticKind::InvalidFunctionPrototype,
        "The prototype is defined here"
    );

    emitter
        .error(1, InvalidFunctionDefinition, "Test", 0u)
        .context(
            dark::DiagnosticContext()
                .insert(")", 2)
                .insert_marker_rel(")", 3)
                .del(dark::MarkerRelSpan(4, 8))
                .error(
                    "prototype does not match the defination",
                    dark::LocRelSpan(0, 2),
                    dark::Span(19, 24)
                )
                .warn(dark::Span(6, 10), dark::Span(25, 27))
                .note("Try to fix the error")
        )
        .sub_diagnostic()
            .warn(0, InvalidFunctionPrototype)
        .build()
        .emit();


}

Note:

You can see more examples inside the example folder.

Outputs/Screenshots

Example 1

Example 2

Example 3

Example 4