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Questions tagged [memmove]

memmove() is a C standard library function to copy a block of memory. It work even if the source and the destination overlap.

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C language wrong output of memove() function?

can't figure out why i got this output from this code. #include #include int main() { char str[] = "I live in NY city"; printf("%s%s\n","The string in array str[] before invokihg the function memmove(): ",str); …
Stanley
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Trying to recode memmove in asm

I am using nasm on Ubuntu 16.04, and I'm currently trying to recode the C memmove() function. Here is my code : BITS 64 global memmove memmove: push rbp mov rbp, rsp xor rcx, rcx while: cmp rcx, rdx je…
souki
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Fast memmove for x86 and +1 shift (for Move-to-front transform)

For fast MTF ( http://en.wikipedia.org/wiki/Move-to-front_transform ) i need faster version of moving a char from inside the array into the front of it: char mtfSymbol[256], front; char i; for(;;) { \\ a very big loop ... i=get_i(); \\ i…
osgx
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C memory overlap?

I am trying to copy the first 16 bytes of a 32 byte string to dest. unsigned char src[32] = "HELLO-HELLO-HELLO-HELLO-HELLO-12"; unsigned char dest[16]; memcpy(dest, src, 16); // COPY printf("%s\n", src); printf("%lu\n",…
desktop
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memmove vs copying backwards

I understand that memmove in C (cstring library) handles overlaps nicely "at the cost of slower runtime" (see this post). I was wondering why this additional runtime cost? It seems to me that any overlap problem could be fixed by copying backwards…
Jonathan H
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Are there optimized versions of memmove for when I know the direction?

Imagine that I am implementing inserting and deleting within a small vector. (If this is C++ then assume further that the vector elements are trivially copyable.) When inserting into the middle of this vector (assuming that I have ascertained that…
John Yates
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Writeablebitmap - scrolling 1 px to the left, what's the best way ? (AKA Where's memmove ?)

I have a writeablebitmap. I want to scroll the contents 1 pixel to the left, and fill in a new pixelrow in the rightmost column. In C++ I'd memmove the entire buffer 1 pixel to the left, and overwrite the last pixel of each line - but I don't know…
Pygmy
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REP MOVSB for overlapped memory

I want to know if there is a difference for instruction rep movsb for overlapped and non-overlapped memory pointers in rdi and rsi? i.e. Is there any difference in implementation of memcpy and memmove via rep movsb instruction? In this documentation…
xperious
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Using std::memmove to work around strict aliasing?

Can std::memmove() be used to "move" the memory to the same location to be able to alias it using different types? For example: #include #include #include #include struct Parts { std::uint16_t v[2u];…
jotik
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Valgrind says "Source and destination overlap in memcpy" about two buffers but they seems to not overlap

LAST EDIT in the end of OP I tested with Valgrind a function used in a project and it says "Source and destination overlap in memcpy" and gives me also "Invalid read" and "Invalid write" errors. I fixed the code in order to not overlap those two…
gc5
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Fixing AddressSanitizer: strcpy-param-overlap with memmove?

I am poking around in an old & quite buggy C program. When compiled with gcc -fsanitize=address I got this error while running the program itself: ==635==ERROR: AddressSanitizer: strcpy-param-overlap: memory ranges [0x7f37e8cfd5b5,0x7f37e8cfd5b8)…
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Memmove in Assembly

I'm trying to put this Memmove C code to assembly and don't get the supposed result. I'm using x86-64 assembly on xubuntu and after debugging for 2 hours, I don't see where I'm wrong. C memmove code: #include extern void * memmove(void…
user9597158
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memmove implementation

In reference to the thread: memmove implementation in C, I did not understand why would there be a memory overlap for 2 different variables? i.e. is this a normal scenario that the compiler allocates same 'common space' to 2 different variables and…
name_masked
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Copy a struct to a specific memory location in Rust

If I have a struct, for example: #[derive(Clone, Copy)] #[repr(C, packed)] pub struct SomeData { a: u16, b: u64, c: u32, d: u16, } How do I copy it to a specific location in memory, e.g. to a point 0x1000 in memory efficiently?…
Hannes Karppila
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/Does/ memmove use an intermediate buffer?

This is more a question out of curiosity than anything important, but I was just wondering about the following snippet in the memmove documentation: Copying takes place as if an intermediate buffer were used (emphasis mine). The formulation…
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