restrict-qualifier Questions
1
Solved
I was thinking about the utility of non-standard __restrict keyword in C and C++ and how its effect can be emulated by carefully declare (disjoint) value objects .
Restrict is usually explained thr...
Midget asked 20/10 at 20:45
1
I'm in the process of updating performance critical libraries to use restrict, as implemented in C++11 by g++ and MSVC with the keyword __restrict.
There are a lot of routines and functions that lo...
Forewent asked 19/9, 2014 at 8:4
1
Solved
Is the C restrict keyword/qualifier transitive through multiple levels of pointer indirection?
For instance, given the following snippet:
struct Bar {
int b;
};
struct Foo
{
struct Bar* bar;
};
...
Grubby asked 22/4 at 19:39
3
The following reasonable program seems to have undefined behavior according to the formal definition of restirct in the C standard:
void positive_intcpy(int * restrict q, const int * restrict p, si...
Savonarola asked 4/1 at 22:49
2
Solved
A restrict-qualified pointer parameter of a function is an effective way to allow compilers to optimize that function:
int f(const int *restrict p) {
int n=*p;
printf("Debug\n");
retur...
Knurl asked 10/1 at 8:18
2
Solved
I know that the restrict qualifier in C specifies that the memory region pointed by two pointers should not overlap. It was my understanding that the Linux (not SUS) prototype for memcpy looks like...
Gracye asked 4/9, 2023 at 5:41
3
Solved
The title says it all. I am curious why is the restrict keyword not part of C++ ? I don't know much about C++, and I'm still not able to find anything online that would give a reason blocking this....
Boorman asked 28/3, 2014 at 23:34
2
Solved
int foo(void *restrict ptr1, void *restrict ptr2)
{
if (ptr1 == ptr2) {
return 1234;
} else {
return 4321;
}
}
restrict implies the the memory pointed to by a pointer is not aliased by any ot...
Sublett asked 20/7, 2023 at 13:54
3
Solved
Given type definitions
struct a { int a; };
struct b { int b; struct a ba;};
and a function taking struct a* a and struct b* b, the type information expresses possible overlap between a->a and ...
Bun asked 27/11, 2022 at 14:26
4
Solved
I have function that receives an array of pointers like so:
void foo(int *ptrs[], int num, int size)
{
/* The body is an example only */
for (int i = 0; i < size; ++i) {
for (int j = 0; j ...
Frigorific asked 7/9, 2011 at 3:8
3
Solved
I was browsing through some documentation and questions/answers and saw it mentioned. I read a brief description, stating that it would be basically a promise from the programmer that the pointer w...
Sheathbill asked 14/4, 2009 at 0:9
3
Solved
In the program I am coding, one of my function declarations goes like this:
bool parse( const sentence & __restrict sentence )
{
// whatever
}
When I compile the code with Microsoft Visual ...
Mooch asked 11/10, 2012 at 13:56
7
I was always unsure; what does the restrict keyword mean in C++?
Does it mean the two or more pointer given to the function does not overlap?
What else does it mean?
Underquote asked 22/4, 2009 at 8:59
1
I was working on highly "vectorizable" code and noted that regarding the C++ __restrict keyword/extension ~, Clang's behavior is different and impractical compared to GCC even in a simple...
Broadspectrum asked 13/12, 2021 at 18:29
1
Solved
Here's the situation:
We received code from an outside source that uses sprintf like strcat. Like this:
char buffer[1024];
sprintf(buffer, "Some text.");
sprintf(buffer, "%s%s",...
Farleigh asked 21/10, 2021 at 15:57
1
Solved
I am attempting some optimization of code, but it is hard to wrap my head around whether "restrict" is useful in this situation or if it will cause problems.
I have a function that is pas...
Exuviae asked 12/8, 2021 at 20:38
1
Solved
In short, restrict is supposed to tell the compiler that the pointers cannot point into the same memory location. Which is very useful for, say, function arguments and further compiler optimization...
Rhyme asked 23/5, 2019 at 21:48
2
Solved
I understand what restrict means, but I'm a little bit confused with such usage/syntax:
#include <stdio.h>
char* foo(char s[restrict], int n)
{
printf("%s %d\n", s, n);
return NULL;
}
in...
Lakeesha asked 9/10, 2018 at 15:25
4
Consider the following code:
void doesnt_modify(const int *);
int foo(int *n) {
*n = 42;
doesnt_modify(n);
return *n;
}
where the definition of doesnt_modify isn’t visible for the compiler. ...
Ivon asked 13/10, 2014 at 18:14
4
Is there any practical difference between the following prototypes?
void f(const int *p);
void f(const int *restrict p);
void f(const int *volatile p);
The section C11 6.7.6.3/15 (final senten...
Bellhop asked 2/3, 2015 at 21:35
3
Solved
Neither gcc 5 nor clang 3.6 give warnings where the constraints of the restrict qualifier are violated, even when called with -Wall. Consider the following code fragment:
extern void f(char *restr...
Formicary asked 5/6, 2015 at 0:2
2
First some references. The C99 Standard says this about restrict in section 6.7.3:
An object that is accessed through a restrict-qualified pointer has a
special association with that pointer. T...
Ontina asked 26/3, 2015 at 10:32
5
Solved
Just wondering: When I add restrict to a pointer, I tell the compiler that the pointer is not an alias for another pointer. Let's assume I have a function like:
// Constructed example
void foo (fl...
Polyandrous asked 19/1, 2009 at 12:30
2
Is there a way to tell a C99 compiler that the only way I am going to access given array is by using myarray[index] ?
Say something like this:
int heavy_calcualtions(float* restrict range1, float*...
Zorina asked 26/9, 2013 at 11:11
1
Solved
Here is some fairly straightforward code, compiled with -O2 (gcc 4.8.5) :
unsigned char * linebuf;
int yuyv_tojpegycbcr(unsigned char * buf, int w)
{
int col;
unsigned char * restrict pix = buf;...
Contexture asked 29/2, 2016 at 12:32
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