C++ coding guidelines

Naming

Naming is somewhat based on Java Naming Convention, the difference is in constants, mainly due to C Preprocessor.

  1. Filenames: should match name of a class or namespace

    NodeEndpoint.h - if there are more classes in file, filename should match the most important

  2. Name of: structs, classes, enums (all non-basic types)

    MyEnum, NodeEndpoint - should be nouns

  3. Static and free function names

    ‘DoSomething’ - should contain verb

  4. Member function names

    bootKey - for accessors and modifiers (no get or set prefix)

    doSomething - for other functions should contain verb

  5. Global, local and class member

    constants, enum fields State_Data_Continue - words capitalized, delimited with an underline ‘_’

  6. Macros, #defines

    INVALID_SIZE_TMAX_ULONGLONG - word in upper-case, delimited with underline ‘_’

  7. Variables, fields - same as methods

    bytesSend, headlessCamelCase

  8. Prefix class members/fields with an m_ (I actually haven’t been following that rule for a long time, but it makes reviewing the code much faster - especially when looking at commits, not within an IDE)

  9. Prefix pointers with a “p” both smart and raw

  10. Struct fields should be UpperCamelCase

  11. Do not start any variables/function/method names with an underscore

  12. If you pass size of an array somewhere, always give the size variable a name, that suggest what it’s actually is:

    1. So if you actually expect number of elements, use name like size_t foobarCount (eventually foobarLength)

    2. If you want number of bytes use size_t foobarSize

Includes

  1. Always use “/” in includes and NEVER “\”, (C standard WG14/N1256 point 6.4.7, C++ standard ISO/IEC 14882:2003 point 2.8, C++ standard ISO/IEC 14882:2011 (from working draft N3225) point 2.9)

  2. Number of include files in header file should be minimal, that is: ONLY, that what’s actually needed in .h

    What’s needed in .cpp file should only be included in .cpp.

  3. Order of includes (top-down)

    1. OWN (local ones)

    2. Project common

    3. Shared/common <core/...>

    4. System/STL

Nice link for further reading: http://www.topology.org/linux/include.html

if/for

  • Do not use such a construct when for doesn’t have a body

    for (a; b; c);
    

    Instead use

    for (a; b; c) {}
    

This leaves clear intention of what you had in mind.

Operators

  • In case of operators please put additional space before and after them. This makes code much more readable.

    This should be always used in case of =, ==, !=, &&, ||. So this one’s ok:

    for (size_t j = 0; j < foo.size() - x * 4; ++j)
    

    While this one is not:

    for (size_t j=0; j<foo.size()-x*4; ++j)
    

Spaces

  • Always put a space after semicolon ‘;’ in for, that is ok:

    for (size_t j = 0; j < foo.size() - 1; ++j)
    

    This one’s not:

    for (size_t j = 0;j < sections.size();++j)
    
  • Always put a space after coma ‘,’ in function args, like:

    outputAsciiString(buffer, something, elsewhere);
    

    Not:

    outputAsciiString(buffer,something,elsewhere);
    
  • Do NOT leave whitespaces at line-endings (here’s a regex for “Quick Replace” in visual studio: [ ]+$)

Types

  • size_t should be used whenever dealing with data size (in many cases auto is fine too):

    • The result of sizeof() is size_t

    • Difference between pointer types is always size_t

    • Index of an element in an array should be of size_t type

    • The result of strlen() should usually be size_t

    • Most STL containers uses size_t as default size, count, length and index type

  • Please use types defined in stdint.h (uint8_t, uint16_t, uint32_t, etc.)

Disputable:

  • Please avoid using signed types and signed math unless it’s really necessary and reasonable.

Classes, Methods and Members

  • Classes should be named using CamelCase (first letter capital)

  • Class order (disputable):

    1. Private constants (as they are usually used early)

    2. Public constants

    3. Methods (if possible public, protected, private)

    4. Fields

      1. Public members (should probably be used only for POD types)

      2. Protected members

      3. Private members

Arguments

  • Avoid passing arguments as pointers (reference is always preferred) unless it’s really intended and needed.

  • Use const references or const types when possible.

Special Names

  • BlockChain not Blockchain

  • Timestamp not TimeStamp

  • Filesystem not FileSystem

  • configuration for class names

  • config for variable names

Style

Indents

  1. Single indent for block opening

  2. Continuations use double indent

  3. Initializer list, and ctors/function/method arguments, have double indent

Example 1.

for (auto&& pEntity : entities) {
    singleEntityVector[0] = pEntity;
    auto result = dispatcher.dispatch(m_config.ValidationPolicy, singleEntityVector);
    m_config.pObserver->notify(*pEntity, observerContext);
}

Example 2.

CATAPULT_LOG(debug) << "comparing chain scores: " << localScore << " (local) vs "
    << remoteScore << " (remote)";
return pState
    && pState->ImportanceInfo.Importance > Importance(0)
    && pState->Balances.get(Xem_Id) >= minHarvestingBalance;

Example 3.

// mind the double indent for method arguments
static thread::future<std::unique_ptr<model::Block>> BlockAt(
        Height height,
        const io::BlockStorageView& storage) {
    if (Height(0) == height || storage.chainHeight() < height) {
        auto exception = CreateHeightException("unable to get block at height", height);
        return thread::make_exceptional_future<std::unique_ptr<model::Block>>(exception);
    }

    return thread::make_ready_future(storage.loadBlock(height));
}

Bracing style

empty body, short

Foo() : m_value(0)
{}

empty body, long

// two indents
Foo(very arguments, much wow)
        : m_value(0)
        , m_xman(professor)
{}

body, short

Foo() : m_value(0) {
    // body
}

body, long

// two indents
Foo(very arguments, much wow)
        : m_value(0)
        , m_xman(professor) {
    // body
}

Last updated by Xavi Artigas on 2021‑11‑09.

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