All Language Lawyer Solutions on Gang of Coders

Total of 187 Language Lawyer Solutions

Why are arbitrary target expressions allowed in for-loops?

PythonFor LoopLanguage Lawyer

Does initialization entail lvalue-to-rvalue conversion? Is `int x = x;` UB?

C++InitializationUndefined BehaviorLanguage Lawyer

Using `throw;` on a modified exception

C++ExceptionException HandlingLanguage LawyerThrow

Does a[a[0]] = 1 produce undefined behavior?

CLanguage LawyerC99Undefined Behavior

Is std::is_unsigned<bool>::value well defined?

C++BooleanLanguage LawyerC++14Unsigned

Are function return values automatic objects and thus guaranteed to be destructed?

C++Exception HandlingReturnReturn ValueLanguage Lawyer

Why is derived class move constructible when base class isn't?

C++C++11Language LawyerMove SemanticsMove Constructor

reinterpret_cast creating a trivially default-constructible object

C++C++11Language LawyerC++17

Why is the destructor called for an object that is not deleted?

C++Language Lawyer

Do all pointers have the same size in C++?

C++PointersLanguage LawyerVoid Pointers

Strange "->* []" expression in C++ source code of cpp.react library

C++C++11Language LawyerOperator Arrow-Star

Do distinct functions have distinct addresses?

C++Function PointersLanguage LawyerOne Definition-RuleComdat Folding

Deleted default constructor. Objects can still be created... sometimes

C++C++14Language LawyerList InitializationAggregate Initialization

The behaviour of floating point division by zero

C++Floating PointLanguage LawyerUndefined BehaviorDivide by-Zero

Is ++*ptr++ undefined behaviour in c++?

C++Language Lawyer

What does the standard say about how calling clear on a vector changes the capacity?

C++VectorLanguage Lawyer

Incomplete type in nested name specifier

C++Language Lawyer

Accessing attributes on literals work on all types, but not `int`; why?

PythonPython 2.7Python 3.xLanguage Lawyer

Is sizeof(void()) a legal expression?

C++Language LawyerSizeofVoid

Constructor reference - no warning when generics array is created

JavaGenericsJava 8Language Lawyer

Is stateful metaprogramming ill-formed (yet)?

C++Language LawyerMetaprogrammingC++17

A positive lambda: '+[]{}' - What sorcery is this?

C++C++11LambdaOperator OverloadingLanguage Lawyer

When is it valid to access a pointer to a "dead" object?

CPointersLanguage LawyerUndefined Behavior

Why are are std::allocator's construct and destroy functions deprecated in c++17?

C++Memory ManagementLanguage LawyerAllocatorC++17

Can C++ code be valid in both C++03 and C++11 but do different things?

C++C++11Language LawyerC++03

Does the C standard permit assigning an arbitrary value to a pointer and incrementing it?

CPointersLanguage LawyerPointer Arithmetic

Why is unique_ptr not equality_comparable_with nullptr_t in C++20?

C++Language LawyerC++20C++ Concepts

Is it spread "syntax" or the spread "operator"?

JavascriptEcmascript 6Language LawyerSpread Syntax

Ternary operator implicit cast to base class

C++Language LawyerC++17Ternary OperatorImplicit Conversion

Access to protected member through member-pointer: is it a hack?

C++Language LawyerProtectedAccess SpecifierMember Pointers

Is std::memcpy between different trivially copyable types undefined behavior?

C++Language LawyerC++17Undefined BehaviorStrict Aliasing

Why can const char* const & = "hello" compile?

C++ReferenceConstantsLanguage Lawyer

Is it possible to get a pointer to one subobject via a pointer to a different, unreleated subobject?

C++PointersLanguage LawyerC++17Offsetof

Why must I provide 'operator ==' when 'operator <=>' is enough?

C++Language LawyerC++20Language DesignSpaceship Operator

Is `long` guaranteed to be at least 32 bits?

C++StandardsLong IntegerLanguage Lawyer

Is &errno legal C?

CLanguage LawyerErrno

Is a moved-from vector always empty?

C++C++11VectorLanguage LawyerMove Semantics

Is C++ allowed to increase the derived class size if there're no new member variables compared to the base class?

C++InheritanceSizeofLanguage Lawyer

Why is S::x not odr-used?

C++Language LawyerC++17

What's the meaning of "reserved for any use"?

C++CLanguage LawyerC Standard-Library

Difference between i++ and (i)++ in C

CLanguage LawyerIncrementEvaluation

Do std::min(0.0, 1.0) and std::max(0.0, 1.0) yield undefined behavior?

C++Floating PointLanguage LawyerUndefined BehaviorC++ Standard-Library

Why is std::move not [[nodiscard]] in C++20?

C++C++17Language LawyerC++20Nodiscard

Absolute value abs(x) using bitwise operators and Boolean logic

C++CBit ManipulationLanguage LawyerAbsolute Value

Will std::string always be null-terminated in C++11?

C++StringC++11Language LawyerNull Terminated

Repeated typedefs - invalid in C but valid in C++?

C++CTypedefLanguage Lawyer

Why is it not possible to overload class templates?

C++TemplatesOverloadingTemplate SpecializationLanguage Lawyer

Is main a valid Java identifier?

JavaLanguage LawyerMainIdentifier

Is the "lazy man's enable_if" legal C++?

C++C++11Visual C++Language LawyerSfinae

What is the name of this unusual C++ template feature used by Boost.Spirit?

C++TemplatesC++11Language LawyerBoost Spirit

C++20 bit_cast vs reinterpret_cast

C++Language LawyerType AliasC++20

Pointer arithmetics with two different buffers

C++PointersLanguage LawyerPointer Arithmetic

Why does left shift operation invoke Undefined Behaviour when the left side operand has negative value?

C++CLanguage LawyerUndefined BehaviorBit Shift

Different Pointer Arithmetic Results when Taking Address of Array

CPointersLanguage Lawyer

Why is f(i = -1, i = -1) undefined behavior?

C++Language LawyerUndefined Behavior

What are Rust's exact auto-dereferencing rules?

RustReferenceLanguage Lawyer

In CSS Flexbox, why are there no "justify-items" and "justify-self" properties?

CssFlexboxLanguage LawyerW3c

Valid, but worthless syntax in switch-case?

CSwitch StatementLanguage Lawyer

What made i = i++ + 1; legal in C++17?

C++Language LawyerC++17

Does C++11, 14, 17 or 20 introduce a standard constant for pi?

C++C++11C++14Language LawyerC++17

What happens if you static_cast invalid value to enum class?

C++Language Lawyer

Optimizing away a "while(1);" in C++0x

C++LoopsC++11Language LawyerUndefined Behavior

Is the operation "false < true" well defined?

C++BooleanLanguage LawyerComparison Operators

How do I make an infinite empty loop that won't be optimized away?

CClangLanguage LawyerCompiler Optimization

Accessing inactive union member and undefined behavior?

C++Undefined BehaviorLanguage LawyerUnions

C++ zero initialization - Why is `b` in this program uninitialized, but `a` is initialized?

C++InitializationLanguage Lawyer

Copy/move assignment in std::vector::erase() and std::deque::erase()

C++Language LawyerC++14

How does this piece of code determine array size without using sizeof( )?

CArraysSizeLanguage LawyerPointer Arithmetic

Is null reference possible?

C++ReferenceNullLanguage Lawyer

Is it safe to push_back an element from the same vector?

C++VectorReferenceLanguage LawyerPush Back

What is "callback hell" and how and why does RX solve it?

JavascriptCallbackLanguage LawyerReactive ProgrammingRxjs

Lambda returning itself: is this legal?

C++LambdaLanguage LawyerC++17Auto

Definition of "==" operator for Double

C#.NetLanguage Lawyer

Is using if (0) to skip a case in a switch supposed to work?

C++CIf StatementSwitch StatementLanguage Lawyer

When does invoking a member function on a null instance result in undefined behavior?

C++Undefined BehaviorLanguage LawyerStandards ComplianceNull Pointer

Lambda capture and parameter with same name - who shadows the other? (clang vs gcc)

C++C++11LambdaLanguage LawyerShadowing

Why does the delete[] syntax exist in C++?

C++Memory ManagementSyntaxLanguage LawyerStandards

Why does the ternary operator with commas evaluate only one expression in the true case?

C++Language LawyerOperator PrecedenceConditional Operator

When using C headers in C++, should we use functions from std:: or the global namespace?

C++Language LawyerStd

Program being compiled differently in 3 major C++ compilers. Which one is right?

C++Language Lawyer

Is passing a C++ object into its own constructor legal?

C++ClassConstructorLanguage LawyerUndefined Behavior

Does C++20 mandate source code being stored in files?

C++Language LawyerC++20Std Source-Location

std::ignore with structured bindings?

C++C++17Language LawyerStructured BindingsStd Tie

Confusion about array initialization in C

CArraysInitializationLanguage Lawyer

Efficient unsigned-to-signed cast avoiding implementation-defined behavior

C++CastingIntegerLanguage LawyerInteger Overflow

Does "Undefined Behavior" really permit *anything* to happen?

C++CLanguage LawyerUndefined Behavior

Have there ever been silent behavior changes in C++ with new standard versions?

C++Language LawyerStandardization

Effectively final vs final - Different behavior

JavaLanguage LawyerFinalJlsEffectively Final

C++11 introduced a standardized memory model. What does it mean? And how is it going to affect C++ programming?

C++MultithreadingC++11Language LawyerMemory Model

Why is "using namespace X;" not allowed at class/struct level?

C++NamespacesUsingLanguage Lawyer

C++ - Why static member function can't be created with 'const' qualifier

C++StaticLanguage LawyerConst Method

Is "else if" a single keyword?

C++SyntaxLanguage Lawyer

Is it still safe to delete nullptr in c++0x?

C++NullLanguage LawyerDelete Operator

How can a program with a global variable called main instead of a main function work?

C++MainLanguage Lawyer

When is a private constructor not a private constructor?

C++C++11Language LawyerDefault ConstructorAggregate Initialization

When do extra parentheses have an effect, other than on operator precedence?

C++C++11Language LawyerParenthesesC++ Faq

Does this code from "The C++ Programming Language" 4th edition section 36.3.6 have well-defined behavior?

C++C++11Language LawyerOperator PrecedenceUnspecified Behavior

Printing null pointers with %p is undefined behavior?

CLanguage LawyerC99Undefined BehaviorC11

How many levels of pointers can we have?

C++CPointersLanguage LawyerLimit

Why do (only) some compilers use the same address for identical string literals?

C++Language LawyerString LiteralsString Interning

Error when using in-class initialization of non-static data member and nested class constructor

C++C++11Language Lawyer

When does type information flow backwards in C++?

C++TypesLanguage LawyerC++17Type Deduction

Is 'auto const' and 'const auto' the same?

C++C++11Language LawyerConstantsAuto

Can branches with undefined behavior be assumed unreachable and optimized as dead code?

C++Language LawyerUndefined BehaviorDead CodeUnreachable Code

trap representation

C++CVisual Studio-2010GccLanguage Lawyer

Is this a known pitfall of C++11 for loops?

C++For LoopC++11Language LawyerForeach

Why are async state machines classes (and not structs) in Roslyn?

C#.NetLanguage LawyerRoslyn

Different behaviour of comma operator in C++ with return?

C++ReturnLanguage LawyerOperator PrecedenceComma Operator

Why are references not "const" in C++?

C++ReferenceConstantsLanguage LawyerDecltype

Why do C and C++ allow the expression (int) + 4*5?

C++CCastingLanguage Lawyer

Is a pointer with the right address and type still always a valid pointer since C++17?

C++PointersC++14Language LawyerC++17

Pure Functions: Does "No Side Effects" Imply "Always Same Output, Given Same Input"?

JavascriptFunctional ProgrammingLanguage LawyerPure Function

Is it legal for source code containing undefined behavior to crash the compiler?

C++Language LawyerUndefined Behavior

Is `new` in `new int;` considered an operator?

C++Language Lawyer

Is it guaranteed to be safe to perform memcpy(0,0,0)?

CMemcpyLanguage LawyerNull Pointer

Can argc be zero on a POSIX system?

CPosixLanguage LawyerMain

Can code that will never be executed invoke undefined behavior?

CLanguage Lawyer

Is it allowed for a compiler to optimize away a local volatile variable?

C++Language LawyerC++17Volatile

Will consteval functions allow template parameters dependent on function arguments?

C++Language LawyerConstexprC++20Class Template

What is the size of void?

C++CLanguage LawyerSizeof

Capturing a reference by reference in a C++11 lambda

C++C++11LambdaLanguage Lawyer

How can this structure have sizeof == 0?

C++Language LawyerSizeof

What is difference between const and non const key?

C++KeyLanguage LawyerKey ValueStdmap

Take the address of a one-past-the-end array element via subscript: legal by the C++ Standard or not?

C++CStandardsLanguage Lawyer

Different cast operator called by different compilers

C++Language Lawyer

Can I use NULL as substitution for the value of 0?

C++CPointersNullLanguage Lawyer

Why is 019 not a JavaScript syntax error? Or why is 019 > 020

JavascriptGrammarLanguage LawyerEcmascript 5Javacc

Why is a const variable sometimes not required to be captured in a lambda?

C++LambdaConstantsLanguage Lawyer

Cv-qualifications of prvalues (revisited)

C++Language LawyerC++17Temporary ObjectsPrvalue

What are the valid signatures for C's main() function?

CLanguage LawyerSignatureEntry PointFunction Prototypes

Type of `this` in static member function?

C++C++11Language Lawyer

Is masking before unsigned left shift in C/C++ too paranoid?

C++CLanguage LawyerUndefined BehaviorInteger Arithmetic

Why would the behavior of std::memcpy be undefined for objects that are not TriviallyCopyable?

C++C++11Language LawyerMemcpyObject Lifetime

Does C or C++ guarantee array < array + SIZE?

C++CLanguage Lawyer

Is the compiler allowed to optimize out heap memory allocations?

C++GccOptimizationClangLanguage Lawyer

What are the common undefined/unspecified behavior for C that you run into?

CLanguage LawyerUndefined BehaviorUnspecified Behavior

std::tuple sizeof, is it a missed optimization?

C++TuplesLanguage LawyerPadding

Why don't I need to specify "typename" before a dependent type in C++20?

C++TemplatesLanguage LawyerC++20Typename

Why was the space character not chosen for C++14 digit separators?

C++Language LawyerC++14Digit

Is it legal to compare dangling pointers?

C++PointersLanguage LawyerDangling Pointer

Why does the compiler match "char" to "int" but not "short"?

C++Type ConversionOverloadingLanguage Lawyer

Is copying 2D arrays with "memcpy" technically undefined behaviour?

C++CMultidimensional ArrayLanguage LawyerUndefined Behavior

Is std::stoi actually safe to use?

C++StandardsLanguage Lawyer

Can using a lambda in header files violate the ODR?

C++C++11LambdaLanguage LawyerOne Definition-Rule

Return void type in C and C++

C++CGccClangLanguage Lawyer

Initializing an array of zeroes

C++ArraysInitializationLanguage Lawyer

Exact moment of "return" in a C++-function

C++Language LawyerC++17Object LifetimeCopy Elision

How do I specify an integer literal of type unsigned char in C++?

C++IntegerConstantsLanguage Lawyer

What is the behavior of printing NULL with printf's %s specifier?

CLinuxLanguage LawyerCompiler Bug

Could a C++ implementation, in theory, parallelise the evaluation of two function arguments?

C++Language Lawyer

Why is a double semicolon a SyntaxError in Python?

PythonSyntax ErrorLanguage Lawyer

De Morgan's Law optimization with overloaded operators

C++Operator OverloadingLanguage LawyerCompiler Optimization

Could it be the case that sizeof(T*) != sizeof(const T*)?

C++Language Lawyer

int a[] = {1,2,}; Why is a trailing comma in an initializer-list allowed?

C++SyntaxGrammarLanguage Lawyer

Why isn't `std::initializer_list` defined as a literal type?

C++Language LawyerC++14Initializer ListConstexpr

Pure virtual functions may not have an inline definition. Why?

C++Pure VirtualLanguage Lawyer

Using std::bind with member function, use object pointer or not for this argument?

C++C++11Language Lawyer

Can the compiler optimize from heap to stack allocation?

C++Memory ManagementLanguage LawyerCompiler Optimization

Is a C compiler allowed to coalesce sequential assignments to volatile variables?

CLanguage LawyerCompiler OptimizationVolatile

In C++, does initializing a global variable with itself have undefined behaviour?

C++Language LawyerUndefined Behavior

reinterpret_cast between char* and std::uint8_t* - safe?

C++C++11Language LawyerStrict AliasingUint8t

Redefining lambdas not allowed in C++11, why?

C++C++11LambdaLanguage Lawyer

Has C++ standard changed with respect to the use of indeterminate values and undefined behavior in C++14?

C++C++11Language LawyerUndefined BehaviorC++14

Do we really need "enum class" in C++11?

C++EnumsC++11Language Lawyer

Why does clang's stdbool.h contain #define false false

C++ClangLanguage Lawyer

If two objects are declared in a single line, in which order are they constructed?

C++Language LawyerDeclarationObject Construction

Changed rules for protected constructors in C++17?

C++ConstructorLanguage LawyerC++17Protected

Fortran: integer*4 vs integer(4) vs integer(kind=4)

FortranLanguage Lawyer

Are int8_t and uint8_t intended to be char types?

C++C++11IostreamLanguage LawyerStandard Library

Is 0 an octal or a decimal in C?

CLanguage LawyerLiteralsOctal

Is x = std::move(x) undefined?

C++C++11Language LawyerC++14

Is unevaluated division by 0 undefined behavior?

C++CLanguage Lawyer

Class static variable initialization order

C++ScopeLanguage Lawyer

Why does C++11 contain an odd clause about comparing void pointers?

C++C++11PointersLanguage LawyerComparison Operators

Why did the range based 'for' loop specification change in C++17?

C++For LoopLanguage LawyerC++17

Does new char actually guarantee aligned memory for a class type?

C++C++11Language Lawyer

Does `sizeof` *really* evaluate to a `std::size_t`? Can it?

C++C++11StdLanguage Lawyer

Do C++ enums Start at 0?

C++EnumsLanguage LawyerEnumerationOrdinal

What is the type of null literal?

C#.NetLanguage Lawyer

Does &((struct name *)NULL -> b) cause undefined behaviour in C11?

CLanguage LawyerC11Offsetof

C++ switch statement expression evaluation guarantee

C++StandardsLanguage Lawyer

Why does `int ;` compile fine in C, but not in C++?

C++CGccLanguage LawyerVariable Declaration

Addition assignment += behavior in expression

JavascriptJavaLanguage LawyerCompound Assignment

Why does the order of template argument substitution matter?

C++TemplatesC++11Language LawyerC++14

What changes introduced in C++14 can potentially break a program written in C++11?

C++C++11C++14Language LawyerC++ Faq

Does a declaration using "auto" match an extern declaration that uses a concrete type specifier?

C++Language LawyerExternAuto

Is ++x %= 10 well-defined in C++?

C++Language LawyerUndefined BehaviorEvaluation