Comment by CPlus on Why is type-punning at compile-time a no-go?
@kaya3 I find it hard to imagine how 'little-endian at runtime but big-endian at compile-time' could be, for example, the compiler has to know ahead of time what endian to put integer constants in the...
View ArticleComment by CPlus on Why do compilers typically convert code into abstract...
@apropos So does that mean an optimizing C compiler would have more 'effect' on C code than an optimizing assembly compiler would have on assembly?
View ArticleComment by CPlus on Are there any languages where conditions are not...
@kaya3 What if you don't have boolean types at all, and all the 'logical operators' and comparisons are just part of the if statement syntax, and do not exist outside of one? Are any languages like that?
View ArticleWhy would accessing uninitialized memory necessarily be undefined behavior?
In C, accessing any indeterminate/uninitialized memory is undefined behavior, period. Even in the case that the type in question is guaranteed to have no trap representations, such as unsigned char or...
View ArticleWhy are mixed declarations more challenging to implement than forcing all...
C89 had a requirement that all declarations must appear at the top of the scope before any statements:int func(void) { int x = 10; f(); int y = 20; // Invalid // ...}However this requirement was easy...
View ArticleAnswer by CPlus for What are the advantages/disadvantages of null-terminated...
Short String OptimizationOne way one could save having to allocate a separate buffer at a separate location is short string optimization. The idea is if the string is shorter than the size of a...
View ArticleWhy are symbols (especially static/internal symbols) necessary?
Compiled languages seem to always have to attach some name to any global object, such as a function or global variable, even after they are compiled, but not local variables. As such, languages such as...
View ArticleAnswer by CPlus for Why do so many programming languages not have a...
One possible reason why C does this is because C has a concept of hosted and freestanding implementations. If an implementation is freestanding, then the standard libraries do not need to be provided....
View ArticleIs there any particular reason to only include 3 out of the 6 trigonometry...
Most languages seem to only have sincos and tan. While the other 3 are just 1/cos1/sin and 1/tan, is there any way that supporting the other 3 directly could be faster than calculating one and then...
View ArticleAnswer by CPlus for What are the pros and cons of interpreted programming...
The ability to product self-modifying code, such as by producing strings that are then executed as if they are a piece of code of said language, are trivial to do in an interpreted language, but not so...
View ArticleAnswer by CPlus for Types and variables in a different namespace
Function call or type cast?One example of an ambiguous statement in a C-style language that supports type names and object names overlapping is if there is a function or function pointer called x and a...
View ArticleTypes and variables in a different namespace
What would it take to design a language that permitted construct such as below?int int = 10;Such a language would need to be able to infer contextually whether a type name or an expression is expected....
View ArticleIs there any way a Java-like language could implement immutable primitive...
I asked: What prevents Java from having immutable primitive arrays? a while back and got an answer: Because immutable primitive arrays would typically require checking some immutable flag every time a...
View ArticleWhat are the drawbacks of allowing implicit boolean/integer conversions?
Some languages (C, C++, JavaScript, Python) allow one to use integers as booleans and vice versa:int x;if (x) // Equivalent to: x != 0 y();Or:int x = 10 + (y > 10); // Equivalent to: y > 10 ? 11...
View ArticleWhat are the advantages and disadvantages of the callee versus caller...
This is more a question about compiler design than language design, but in low level languages, when a function is called, the parameters are pushed onto the stack, and when the function returns, the...
View ArticleHow can memory addresses be compile-time constants?
In C the memory address of a statically allocated object or a function is considered compile-time constant. For example this is valid code:static int x;static int *const p = &x;static const char...
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Why is truncated or non-Euclidean division/modulo the norm?
Related to, but not the same question: Distinguishing modulo (Euclidean division) from remainderThere are multiple ways a modulo operation can be performed. Most implementations, in C, for example, use...
View ArticleWhat are the implications of a 'packed' keyword/feature?
I am bothered by the fact that, in C, struct types can be arbitrarily large. We have no control over their memory layout except for the fact that the first member is always at the beginning of the...
View ArticleWhy would a language have a concept of undefined behavior instead of raising...
Certain constructs or conditions in programming just are not allowed. Languages such as Java or Swift handle these by raising an error when encountered. C and C++ on the other hand say 'Anything could...
View ArticleWhat prevented fopen() from utilizing macros/flags but not fseek()?
In C, fopen() uses string literals such as "r" or "r+" or "w" to specify the mode with which to open a file. One possible reason for this I read is at the time C was so new that there might not have...
View ArticleWhat are the advantages of strings and character arrays being different?
In many languages such as Java, strings and character arrays are distinct types. In Java one must use toCharArray() in order to use array semantics on strings.In C, strings and character arrays are...
View ArticleEntry point of low level languages
I noticed C defines the entry point as a main() function. So does Java. So does C++ (or not, because functions called as global variable initializers are called before main(). I was wondering. Is there...
View ArticleWhat are the ways compilers recognize complex patterns?
This answer is an example of a compiler recognizing that a complex expression is equivalent to a single operation:uint8_t pcnt64(uint64_t n) { n = n - ((n >> 1) & 0x5555555555555555ULL); n =...
View ArticleHow would I describe an expression separately from a statement?
I have thought about how I could specify an expression separate from a statement.A fragment of code that resolves to a value.But void expressions are still expressions but do not really resolve to a...
View ArticleWhen can widening conversions cause problems?
I can understand the reason for raising a warning or error when you try to convert a wider integer type to a narrower one, due to the loss of precision.Some C compilers will warn about this:uint32_t x...
View ArticleComment by CPlus on Why short and long and double and similar instead of...
I was not aware of such a requirement. I thought the Standard said that floating point format is implementation-defined.
View ArticleComment by CPlus on Why short and long and double and similar instead of...
@NateEldredge In hindsight in those cases, I find what C99 did to be the most logical, having the ambiguous, but required intlong etc., but also offering the unambiguous int32_tint64_t but only...
View ArticleComment by CPlus on Is there any way a Java-like language could implement...
What is meant by if we cannot prove linearity, freezing would fall back to copying?
View ArticleWhat optimizations are possible with unsequenced operators?
In C, most binary operators do not specify which operand will be evaluated first:int x(void) { putchar('x'); return 10;}int y(void) { putchar('y'); return 10;}// ...x()+y(); // Unspecified behavior as...
View ArticleWhy did C99 have to add the underscored keywords for _Bool _Complex...
C99 introduced the following keywords: _Bool_Complex_ImaginaryinlinerestrictWhy _Bool_Complex and _Imaginary instead of just boolcomplex and imaginary? To preserve backwards compatibility for existing...
View ArticleComment by CPlus on What are the advantages if caller is responsible for...
This question is similar to: What are the advantages and disadvantages of the callee versus caller clearing the stack after a call?. If you believe it’s different, please [edit] the question, make it...
View ArticleWhy would a language need to have trap representations?
In C there is a concept of trap representations, or non-value representations. If such a value is produced or used, immediate undefined behavior is invoked. This is one of the dangers of using...
View ArticleHow do modern compilers choose which variables to put in registers?
C has the register keyword, originally designed as a hint to the compiler that a variable should be placed in a register rather than on the stack. However this is generally considered an unneeded...
View ArticleComment by CPlus on Decimal point as a binary operation
I am not sure why this would simplify the PL design.
View ArticleComment by CPlus on Decimal point as a binary operation
With no leading zeros, 10^-c would be just one, which is not necessarily desirable.
View ArticleComment by CPlus on What obstacles prevented C and C++ from standardizing π?
But... hex floating point constants are already a thing in C.
View ArticleComment by CPlus on What are the different ways of handling multiple return...
@user That would be the responsibility of the caller to ensure otherwise.
View ArticleComment by CPlus on What syntax could be used to implement both an...
@supercat Squared can be easily emulated by multiplying the number by itself.
View ArticleComment by CPlus on What obstacles prevented C and C++ from standardizing π?
If they can define the sin, asin, tan, atan, etc. functions, they could just define M_PI as having the same value that atan(1)*4 would produce.
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