Memcpy

Memcpy() is a C standard library function used for copying a block of memory bytes from one place to another.

Memmove

Memmove() is a C standard library function to copy a block of memory



Faster platform little

Example

"Memmove instead of memcpy .;memcpy is faster but it s not safe for moving blocks of memory where the source and destination overlap"

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Mempcy fail to copy all data

"Bad news is that the asmlib version of memmove is slower than the glibc version it is now running at the 300ms mark on par with the glibc version of memcpy"

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Poor memcpy Performance on Linux

"Memcpy is still a little bit slower than memmove"

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Why is memmove faster than memcpy?

"Why is memcpy so much slower than memmove or hand rolled copy on the server"

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Poor memcpy Performance on Linux

"This means that memmove might be very slightly slower than memcpy as it cannot make the same assumptions"

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What is the difference between memmove and memcpy?

"Why does memcpy perform slower than memmove on my system"

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Unexpected performance from memcpy and memmove

"And it said memmove might be very slightly slower than memcpy"

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Performance of memmove compared to memcpy twice?

"So in what platform and how memcpy can be significantly faster than memmove if there is none why providing two similiar functions instead of just memmove and lead to a lots of bug"

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In what platform memmove and memcpy can have significant performance difference?

"From reading other so questions such as this or this gives the impression that memcpy should work faster than memmove and intuitively this should be so"

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Unexpected performance from memcpy and memmove

"On some arm platform im working on memmove was 3 times faster than memcpy for short unalligned load"

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Which one to use - memmove() or memcpy() - when buffers don't overlap?

"The question is about is there really any platform where memcpy is faster than memmove"

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In what platform memmove and memcpy can have significant performance difference?

"Edit memmove is 2x faster than memcpy on the server"

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Poor memcpy Performance on Linux

Efficient memmove std

Example

"Memcpy is more efficient than memmove. in general use memmove only if you have to"

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Fastest way to copy small - medium chunks of memory in C++

"As already pointed out in other answers memmove is more sophisticated than memcpy such that it accounts for memory overlaps"

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Memcpy() vs memmove()

"As an aside my c c++ is rusty but is not memcpy more efficient than memmove if you know you don t have overlapping memory"

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Copying only a part of a buffer from native code to Java using JNI

"Memcpy is more efficient than memmove. in your case you most probably are not doing the exact same thing while you run the two functions"

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Why is memmove faster than memcpy?

"std memmove may be very slightly slower than std memcpy emphasis added because it has to first check whether the source and target ranges overlap"

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Performance of memmove compared to memcpy twice?

"Std copy to be more efficient than memcpy or memmove because std"

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What are the condition for the compiler to reduce std::copy to memcpy (memmove)

"Or you can use memmove which permits overlapping memory space memcpy is not safe for overlapping copies;memmove is more efficient than a loop though optimizing compilers may solve that"

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How to remove elements in static array effectively in C

Standard overlapped ub

Example

"While memmove will be only slightly slower than memcpy due to the assumptions it needs to make about the source and destination in memcpy they cannot overlap it should still be far superior to any standard loop"

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Memmove vs. copying individual array elements

"According to the c c++ standard using memcpy with overlapped memory is ub on the other hand memmove is potentially slower"

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How to check that two arbitrary memory ranges are not overlapped in c/c++

Others

Example

However because of additional checks that memmove performs when the buffers are small and surely does not overlap memcpy is better

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Memmove doesn't move

Note that memmove has more overhead than memcpy because memmove has to determine which direction of copying is safe

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C: Memcpy vs Shifting: Whats more efficient?

The memmove function properly handles overlapping source and destination;memcpy is faster on some platforms and can be safely used to copy between strings

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Insert a string into another string efficiently

Memcpy should have that behavior;memmove doesn t by design if the blocks of memory overlap it copies the contents starting at the ends of the buffers to avoid that sort of behavior

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Why is there no Z80 like LDIR functionality in C/C++/rtl?

Libc s memcpy is likely to be much better optimized using larger-than-byte units platform-specific performance tricks example inline assembly sse on x86 etc;there s also memmove which has better specified behavior when the buffers overlap

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Why does memcpy need a const void pointer?

In addition as mats petersson said memmove is cache friendlier than memcpy

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Why is memmove faster than memcpy?

If you know buffers cannot overlap memcpy is fine and may in any given library use optimizations that allow it to be faster than memmove

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Memmove doesn't move

If you know for sure that src and dst don t overlap call memcpy as it won t matter which one you call for the result both will work correctly in that case but memmove will never be faster than memcpy and if you are unlucky it may even be slower so you can only win calling memcpy

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What is the difference between memmove and memcpy?

It is entirely possible that in most implementations the cost of a memmove function call will not be significantly greater than memcpy in any scenario in which the behavior of both is defined

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What are real significant cases when memcpy() is faster than memmove()?

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