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C storage and linkage.

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Joshua Potter 2024-11-30 16:43:44 -07:00
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title: "2024-11-30"
---
- [x] Anki Flashcards
- [ ] KoL
- [x] OGS
- [ ] Sheet Music (10 min.)
- [ ] Korean (Read 1 Story)
* Preliminary notes on [[linkage]].

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---
title: "2024-11-28"
---
- [x] Anki Flashcards
- [x] KoL
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* Notes on [[strings#Copying Functions|memcpy and memmove]].

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@ -500,7 +500,7 @@ END%%
For any sets $A$, $B$, and $C$, $$\begin{align*} A \times (B \cap C) & = (A \times B) \cap (A \times C) \\ A \times (B \cup C) & = (A \times B) \cup (A \times C) \\ A \times (B - C) & = (A \times B) - (A \times C) \end{align*}$$
%%ANKI
Basic
Which of the algebra of sets operators does the Cartesian product distributive over?
Which of the algebra of sets operators does the Cartesian product distribute over?
Back: $\cap$, $\cup$, and $-$
Reference: “Cartesian Product,” in _Wikipedia_, April 17, 2024, [https://en.wikipedia.org/w/index.php?title=Cartesian_product&oldid=1219343305](https://en.wikipedia.org/w/index.php?title=Cartesian_product&oldid=1219343305).
<!--ID: 1718069881718-->

2
notes/c17/alignment.md
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@ -42,7 +42,7 @@ END%%
%%ANKI
Basic
What addresses can a `int` be stored at?
What addresses can an `int` be stored at?
Back: Any address divisible by 4.
Reference: Raymond, Eric. “The Lost Art of Structure Packing.” Accessed November 4, 2024. [http://www.catb.org/esr/structure-packing/](http://www.catb.org/esr/structure-packing/).
<!--ID: 1730831516934-->

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@ -469,7 +469,7 @@ END%%
%%ANKI
Basic
Which library defines `EXIT_SUCCESS`?
Back: `stdlib.h`
Back: `<stdlib.h>`
Reference: Jens Gustedt, _Modern C_ (Shelter Island, NY: Manning Publications Co, 2020).
<!--ID: 1732293415810-->
END%%
@ -477,7 +477,7 @@ END%%
%%ANKI
Basic
Which library defines `EXIT_FAILURE`?
Back: `stdlib.h`
Back: `<stdlib.h>`
Reference: Jens Gustedt, _Modern C_ (Shelter Island, NY: Manning Publications Co, 2020).
<!--ID: 1732293415813-->
END%%
@ -503,7 +503,7 @@ Which library declares the following prototype?
```c
noreturn void exit(int)
```
Back: `stdlib.h`
Back: `<stdlib.h>`
Reference: Jens Gustedt, _Modern C_ (Shelter Island, NY: Manning Publications Co, 2020).
<!--ID: 1732293415823-->
END%%
@ -542,7 +542,7 @@ END%%
%%ANKI
Basic
Which library is `noreturn` defined in?
Back: `stdnoreturn.h`
Back: `<stdnoreturn.h>`
Reference: Jens Gustedt, _Modern C_ (Shelter Island, NY: Manning Publications Co, 2020).
<!--ID: 1732293415846-->
END%%

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---
title: Linkage
TARGET DECK: Obsidian::STEM
FILE TAGS: c17::linkage
tags:
- c17
- linkage
---
## Overview
An identifier declared in different scopes or in the same scope multiple times can be made to refer to the same object or function by a process called **linkage**. There are three kinds of linkage: **external**, **internal**, and **none**.
%%ANKI
Basic
Linkage is a property of what C construct?
Back: Identifiers.
Reference: Jens Gustedt, _Modern C_ (Shelter Island, NY: Manning Publications Co, 2020).
<!--ID: 1733010193273-->
END%%
%%ANKI
Basic
What capability does linkage allow identifiers to perform?
Back: Reference to the same object or function.
Reference: “ISO: Programming Languages - C,” April 12, 2011, [https://port70.net/~nsz/c/c11/n1570.pdf](https://port70.net/~nsz/c/c11/n1570.pdf).
<!--ID: 1733010193275-->
END%%
%%ANKI
Basic
What are the three kinds of linkage?
Back: External, internal, and none.
Reference: “ISO: Programming Languages - C,” April 12, 2011, [https://port70.net/~nsz/c/c11/n1570.pdf](https://port70.net/~nsz/c/c11/n1570.pdf).
<!--ID: 1733010193276-->
END%%
%%ANKI
Basic
External linkage denotes the same object across what?
Back: The entire program.
Reference: “ISO: Programming Languages - C,” April 12, 2011, [https://port70.net/~nsz/c/c11/n1570.pdf](https://port70.net/~nsz/c/c11/n1570.pdf).
<!--ID: 1733010193277-->
END%%
%%ANKI
Basic
Internal linkage denotes the same object across what?
Back: A single translation unit.
Reference: “ISO: Programming Languages - C,” April 12, 2011, [https://port70.net/~nsz/c/c11/n1570.pdf](https://port70.net/~nsz/c/c11/n1570.pdf).
<!--ID: 1733010193278-->
END%%
%%ANKI
Basic
What is the linkage between two different identifiers?
Back: None.
Reference: “ISO: Programming Languages - C,” April 12, 2011, [https://port70.net/~nsz/c/c11/n1570.pdf](https://port70.net/~nsz/c/c11/n1570.pdf).
<!--ID: 1733010193279-->
END%%
%%ANKI
Basic
Which keyword is usually associated with external linkage?
Back: `extern`
Reference: “ISO: Programming Languages - C,” April 12, 2011, [https://port70.net/~nsz/c/c11/n1570.pdf](https://port70.net/~nsz/c/c11/n1570.pdf).
<!--ID: 1733010193280-->
END%%
%%ANKI
Basic
What linkage does a keyword annotated with `extern` have?
Back: Internal or external.
Reference: “ISO: Programming Languages - C,” April 12, 2011, [https://port70.net/~nsz/c/c11/n1570.pdf](https://port70.net/~nsz/c/c11/n1570.pdf).
<!--ID: 1733010193281-->
END%%
%%ANKI
Basic
What linkage does a keyword associated with `static` have?
Back: Internal.
Reference: “ISO: Programming Languages - C,” April 12, 2011, [https://port70.net/~nsz/c/c11/n1570.pdf](https://port70.net/~nsz/c/c11/n1570.pdf).
<!--ID: 1733010193282-->
END%%
%%ANKI
Basic
Which keyword is usually associated with internal linkage?
Back: `static`
Reference: “ISO: Programming Languages - C,” April 12, 2011, [https://port70.net/~nsz/c/c11/n1570.pdf](https://port70.net/~nsz/c/c11/n1570.pdf).
<!--ID: 1733010193283-->
END%%
%%ANKI
Basic
When can an identifier have both external and internal linkage?
Back: When specified in two different translation units.
Reference: “ISO: Programming Languages - C,” April 12, 2011, [https://port70.net/~nsz/c/c11/n1570.pdf](https://port70.net/~nsz/c/c11/n1570.pdf).
<!--ID: 1733010193284-->
END%%
%%ANKI
Basic
Within a translation unit, what happens if an identifer has both external and internal linkage?
Back: Undefined behavior.
Reference: “ISO: Programming Languages - C,” April 12, 2011, [https://port70.net/~nsz/c/c11/n1570.pdf](https://port70.net/~nsz/c/c11/n1570.pdf).
<!--ID: 1733010193285-->
END%%
%%ANKI
Basic
Consider the following translation unit. What is the linkage of `x`?
```c
int x;
```
Back: External.
Reference: “ISO: Programming Languages - C,” April 12, 2011, [https://port70.net/~nsz/c/c11/n1570.pdf](https://port70.net/~nsz/c/c11/n1570.pdf).
<!--ID: 1733010193286-->
END%%
%%ANKI
Basic
Consider the following translation unit. What is the linkage of `foo`?
```c
void foo(void) { }
```
Back: External.
Reference: “ISO: Programming Languages - C,” April 12, 2011, [https://port70.net/~nsz/c/c11/n1570.pdf](https://port70.net/~nsz/c/c11/n1570.pdf).
<!--ID: 1733010193287-->
END%%
%%ANKI
Basic
What is the linkage of an object identifier with file scope and no storage-class specifier?
Back: External.
Reference: “ISO: Programming Languages - C,” April 12, 2011, [https://port70.net/~nsz/c/c11/n1570.pdf](https://port70.net/~nsz/c/c11/n1570.pdf).
<!--ID: 1733010193288-->
END%%
%%ANKI
Basic
*How* do you identify the linkage of an object identifier with file scope and no storage-class specifier?
Back: Its always external.
Reference: “ISO: Programming Languages - C,” April 12, 2011, [https://port70.net/~nsz/c/c11/n1570.pdf](https://port70.net/~nsz/c/c11/n1570.pdf).
<!--ID: 1733010193289-->
END%%
%%ANKI
Basic
What is the linkage of a function identifier with file scope and no storage-class specifier?
Back: Internal or external.
Reference: “ISO: Programming Languages - C,” April 12, 2011, [https://port70.net/~nsz/c/c11/n1570.pdf](https://port70.net/~nsz/c/c11/n1570.pdf).
<!--ID: 1733010193290-->
END%%
%%ANKI
Basic
Consider the following translation unit. What is the linkage of `foo`?
```c
static void foo(void);
extern void foo(void);
```
Back: Internal.
Reference: “ISO: Programming Languages - C,” April 12, 2011, [https://port70.net/~nsz/c/c11/n1570.pdf](https://port70.net/~nsz/c/c11/n1570.pdf).
<!--ID: 1733010193291-->
END%%
%%ANKI
Basic
Consider the following translation unit. What is the linkage of `foo`?
```c
extern void foo(void);
static void foo(void);
```
Back: N/A. Undefined behavior.
Reference: “ISO: Programming Languages - C,” April 12, 2011, [https://port70.net/~nsz/c/c11/n1570.pdf](https://port70.net/~nsz/c/c11/n1570.pdf).
<!--ID: 1733010193292-->
END%%
%%ANKI
Basic
Consider the following translation unit. What is the linkage of `foo`?
```c
void foo(void);
static void foo(void);
```
Back: N/A. Undefined behavior.
Reference: “ISO: Programming Languages - C,” April 12, 2011, [https://port70.net/~nsz/c/c11/n1570.pdf](https://port70.net/~nsz/c/c11/n1570.pdf).
<!--ID: 1733010193293-->
END%%
%%ANKI
Basic
Consider the following translation unit. What is the linkage of `foo`?
```c
void foo(void);
void foo(void);
```
Back: External.
Reference: “ISO: Programming Languages - C,” April 12, 2011, [https://port70.net/~nsz/c/c11/n1570.pdf](https://port70.net/~nsz/c/c11/n1570.pdf).
<!--ID: 1733010193294-->
END%%
%%ANKI
Basic
*How* do you identify the linkage of a function identifier with file scope and no storage-class specifier?
Back: Its the same as if the function identifier were declared `extern`.
Reference: “ISO: Programming Languages - C,” April 12, 2011, [https://port70.net/~nsz/c/c11/n1570.pdf](https://port70.net/~nsz/c/c11/n1570.pdf).
<!--ID: 1733010193295-->
END%%
%%ANKI
Basic
What is the linkage of a function parameter?
Back: None.
Reference: “ISO: Programming Languages - C,” April 12, 2011, [https://port70.net/~nsz/c/c11/n1570.pdf](https://port70.net/~nsz/c/c11/n1570.pdf).
<!--ID: 1733010193296-->
END%%
%%ANKI
Basic
What is the linkage of a local variable without a storage specified?
Back: None.
Reference: “ISO: Programming Languages - C,” April 12, 2011, [https://port70.net/~nsz/c/c11/n1570.pdf](https://port70.net/~nsz/c/c11/n1570.pdf).
<!--ID: 1733010193297-->
END%%
%%ANKI
Basic
Consider the following translation unit. What is the linkage of the last `x`?
```c
int x;
int main(void) { extern int x; }
```
Back: External.
Reference: “ISO: Programming Languages - C,” April 12, 2011, [https://port70.net/~nsz/c/c11/n1570.pdf](https://port70.net/~nsz/c/c11/n1570.pdf).
<!--ID: 1733010193298-->
END%%
%%ANKI
Basic
Consider the following translation unit. What is the linkage of the last `x`?
```c
int x;
int main(void) { static int x; }
```
Back: Internal.
Reference: “ISO: Programming Languages - C,” April 12, 2011, [https://port70.net/~nsz/c/c11/n1570.pdf](https://port70.net/~nsz/c/c11/n1570.pdf).
<!--ID: 1733010193299-->
END%%
%%ANKI
Basic
Consider the following translation unit. What is the linkage of the last `x`?
```c
extern int x;
int main(void) { static int x; }
```
Back: Internal.
Reference: “ISO: Programming Languages - C,” April 12, 2011, [https://port70.net/~nsz/c/c11/n1570.pdf](https://port70.net/~nsz/c/c11/n1570.pdf).
<!--ID: 1733010193300-->
END%%
%%ANKI
Basic
Consider the following translation unit. What is the linkage of the last `x`?
```c
extern int x;
int main(void) { extern int x; }
```
Back: External.
Reference: “ISO: Programming Languages - C,” April 12, 2011, [https://port70.net/~nsz/c/c11/n1570.pdf](https://port70.net/~nsz/c/c11/n1570.pdf).
<!--ID: 1733010193301-->
END%%
%%ANKI
Basic
Consider the following translation unit. What is the linkage of the last `x`?
```c
static int x;
extern int x;
int main(void) { extern int x; }
```
Back: Internal.
Reference: “ISO: Programming Languages - C,” April 12, 2011, [https://port70.net/~nsz/c/c11/n1570.pdf](https://port70.net/~nsz/c/c11/n1570.pdf).
<!--ID: 1733010193302-->
END%%
%%ANKI
Basic
Consider the following translation unit. What is the linkage of the last `x`?
```c
extern int x;
static int x;
int main(void) { extern int x; }
```
Back: N/A. Undefined behavior.
Reference: “ISO: Programming Languages - C,” April 12, 2011, [https://port70.net/~nsz/c/c11/n1570.pdf](https://port70.net/~nsz/c/c11/n1570.pdf).
<!--ID: 1733010193303-->
END%%
%%ANKI
Basic
Consider the following translation unit. What is the linkage of the last `x`?
```c
extern int x;
int main(void) { int x; }
```
Back: None.
Reference: “ISO: Programming Languages - C,” April 12, 2011, [https://port70.net/~nsz/c/c11/n1570.pdf](https://port70.net/~nsz/c/c11/n1570.pdf).
<!--ID: 1733010193304-->
END%%
%%ANKI
Basic
Consider the following translation unit. What is the linkage of the last `x`?
```c
static int x;
int main(void) { int x; }
```
Back: None.
Reference: “ISO: Programming Languages - C,” April 12, 2011, [https://port70.net/~nsz/c/c11/n1570.pdf](https://port70.net/~nsz/c/c11/n1570.pdf).
<!--ID: 1733010193305-->
END%%
%%ANKI
Basic
Consider the following translation unit. What is the linkage of the last `x`?
```c
void foo(int x) { }
```
Back: None.
Reference: “ISO: Programming Languages - C,” April 12, 2011, [https://port70.net/~nsz/c/c11/n1570.pdf](https://port70.net/~nsz/c/c11/n1570.pdf).
<!--ID: 1733010193306-->
END%%
## Bibliography
* “ISO: Programming Languages - C,” April 12, 2011, [https://port70.net/~nsz/c/c11/n1570.pdf](https://port70.net/~nsz/c/c11/n1570.pdf).
* Jens Gustedt, _Modern C_ (Shelter Island, NY: Manning Publications Co, 2020).

2
notes/c17/pointers.md
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@ -319,7 +319,7 @@ END%%
%%ANKI
Basic
Trap representations are most relevant to what kind of derivied type?
Trap representations are most relevant to what kind of derived type?
Back: Pointers.
Reference: Jens Gustedt, _Modern C_ (Shelter Island, NY: Manning Publications Co, 2020).
<!--ID: 1732397726948-->

232
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@ -0,0 +1,232 @@
---
title: Storage
TARGET DECK: Obsidian::STEM
FILE TAGS: c17::storage
tags:
- c17
---
## Dynamic Allocation
The `<stdlib.h>` header provides the two most prominent functions used for managing dynamic memory: `malloc` and `free`. The former is used to allocate new memory whereas the latter is used to annihilate it.
```c
void* malloc(size_t size);
void free(void*);
```
%%ANKI
Basic
Which standard library header exposes `malloc`?
Back: `<stdlib.h>`
Reference: Jens Gustedt, _Modern C_ (Shelter Island, NY: Manning Publications Co, 2020).
<!--ID: 1732755874715-->
END%%
%%ANKI
Basic
Which standard library header exposes `free`?
Back: `<stdlib.h>`
Reference: Jens Gustedt, _Modern C_ (Shelter Island, NY: Manning Publications Co, 2020).
<!--ID: 1732755874716-->
END%%
%%ANKI
Basic
Why is `malloc` named the way it is?
Back: It stands for **m**emory **alloc**ate.
Reference: Jens Gustedt, _Modern C_ (Shelter Island, NY: Manning Publications Co, 2020).
<!--ID: 1732755874717-->
END%%
%%ANKI
Basic
What two functions are most prominently used for dynamic allocation?
Back: `malloc` and `free`.
Reference: Jens Gustedt, _Modern C_ (Shelter Island, NY: Manning Publications Co, 2020).
<!--ID: 1732755874718-->
END%%
%%ANKI
Cloze
Generally speaking, memory created with {`malloc`} should be deleted with {`free`}.
Reference: Jens Gustedt, _Modern C_ (Shelter Island, NY: Manning Publications Co, 2020).
<!--ID: 1732755874719-->
END%%
%%ANKI
Basic
What three specialized variants of `malloc` are exposed by `<stdlib.h>`?
Back: `calloc`, `realloc`, and `aligned_alloc`.
Reference: Jens Gustedt, _Modern C_ (Shelter Island, NY: Manning Publications Co, 2020).
<!--ID: 1732755874720-->
END%%
%%ANKI
Basic
On success, what does a call to `malloc` return?
Back: A `void*` pointer.
Reference: Jens Gustedt, _Modern C_ (Shelter Island, NY: Manning Publications Co, 2020).
<!--ID: 1732755874721-->
END%%
%%ANKI
Basic
On failure, what does a call to `malloc` return?
Back: A null pointer value.
Reference: Jens Gustedt, _Modern C_ (Shelter Island, NY: Manning Publications Co, 2020).
<!--ID: 1732755874722-->
END%%
%%ANKI
Basic
What are the argument(s) to `malloc`?
Back: The size (in bytes) of the block of memory to allocate.
Reference: Jens Gustedt, _Modern C_ (Shelter Island, NY: Manning Publications Co, 2020).
<!--ID: 1732755874723-->
END%%
%%ANKI
Basic
What is wrong with the following code snippet?
```c
double *d = (double*)malloc(sizeof *d);
```
Back: The return type of `malloc` should not be cast.
Reference: Jens Gustedt, _Modern C_ (Shelter Island, NY: Manning Publications Co, 2020).
<!--ID: 1732755874724-->
END%%
%%ANKI
Basic
What is wrong with the following code snippet?
```c
double *d = malloc(sizeof *d);
```
Back: N/A. This is valid.
Reference: Jens Gustedt, _Modern C_ (Shelter Island, NY: Manning Publications Co, 2020).
<!--ID: 1732755874725-->
END%%
%%ANKI
Basic
What possible error can occur by explicitly casting the return type of `malloc`?
Back: If `<stdlib.h>` isn't imported, older C compilers assume `malloc` returns an `int`.
Reference: Jens Gustedt, _Modern C_ (Shelter Island, NY: Manning Publications Co, 2020).
<!--ID: 1732755874726-->
END%%
%%ANKI
Basic
Without `<stdlib.h>`, an older C compiler might assume what `malloc` declaration?
Back:
```c
int malloc();
```
Reference: Jens Gustedt, _Modern C_ (Shelter Island, NY: Manning Publications Co, 2020).
<!--ID: 1732755874727-->
END%%
%%ANKI
Basic
Within `<stdlib.h>`, what function prototype does `malloc` have?
Back:
```c
void* malloc(size_t size);
```
Reference: Jens Gustedt, _Modern C_ (Shelter Island, NY: Manning Publications Co, 2020).
<!--ID: 1732755874728-->
END%%
%%ANKI
Cloze
Storage allocated through `malloc` is {uninitialized} and has {no type}.
Reference: Jens Gustedt, _Modern C_ (Shelter Island, NY: Manning Publications Co, 2020).
<!--ID: 1732755874729-->
END%%
%%ANKI
Basic
Does the following invoke undefined behavior? Why or why not?
```c
free(0);
```
Back: No. `free` ignores null pointer values.
Reference: Jens Gustedt, _Modern C_ (Shelter Island, NY: Manning Publications Co, 2020).
<!--ID: 1732755874730-->
END%%
%%ANKI
Basic
Does the following invoke undefined behavior? Why or why not?
```c
double d = 0.0;
free(&d);
```
Back: Yes. `d` was not dynamically allocated.
Reference: Jens Gustedt, _Modern C_ (Shelter Island, NY: Manning Publications Co, 2020).
<!--ID: 1732755874731-->
END%%
%%ANKI
Basic
Does the following invoke undefined behavior? Why or why not?
```c
double* d = malloc(sizeof *d);
free(&d);
```
Back: Yes. `d` was not dynamically allocated.
Reference: Jens Gustedt, _Modern C_ (Shelter Island, NY: Manning Publications Co, 2020).
<!--ID: 1732755874732-->
END%%
%%ANKI
Basic
Does the following invoke undefined behavior? Why or why not?
```c
double* d = malloc(sizeof *d);
free(d);
```
Back: No. The address `d` pointed to was dynamically allocated.
Reference: Jens Gustedt, _Modern C_ (Shelter Island, NY: Manning Publications Co, 2020).
<!--ID: 1732755874733-->
END%%
%%ANKI
Basic
Does the following invoke undefined behavior? Why or why not?
```c
double* d = malloc(sizeof *d);
free(d);
d = 0;
free(d);
```
Back: No. `free` ignores null pointer values.
Reference: Jens Gustedt, _Modern C_ (Shelter Island, NY: Manning Publications Co, 2020).
<!--ID: 1732755874734-->
END%%
%%ANKI
Basic
Does the following invoke undefined behavior? Why or why not?
```c
double* d = malloc(sizeof *d);
free(d);
free(d);
```
Back: Yes. `free` should not be invoked on already `free`'d data.
Reference: Jens Gustedt, _Modern C_ (Shelter Island, NY: Manning Publications Co, 2020).
<!--ID: 1732755874735-->
END%%
%%ANKI
Basic
`malloc` and its variants all have the `size` parameter in what position?
Back: The last position.
Reference: Jens Gustedt, _Modern C_ (Shelter Island, NY: Manning Publications Co, 2020).
<!--ID: 1732755874736-->
END%%
## Bibliography
* Jens Gustedt, _Modern C_ (Shelter Island, NY: Manning Publications Co, 2020).

168
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@ -1146,11 +1146,179 @@ Tags: encoding::unicode
<!--ID: 1706976705750-->
END%%
## Copying Functions
The two primary functions used for copying memory are `memcpy` and `memmove`:
```c
void* memcpy(void* restrict s1, const void* restrict s2, size_t n);
void* memmove(void* s1, const void* s2, size_t n);
```
%%ANKI
Basic
What are the two primary functions provided by the standard library for copying memory?
Back: `memcpy` and `memmove`.
Reference: “ISO: Programming Languages - C,” April 12, 2011, [https://port70.net/~nsz/c/c11/n1570.pdf](https://port70.net/~nsz/c/c11/n1570.pdf).
<!--ID: 1732843837986-->
END%%
%%ANKI
Basic
What is the function prototype of `memcpy`?
Back:
```c
void* memcpy(void* restrict s1, const void* restrict s2, size_t n);
```
Reference: “ISO: Programming Languages - C,” April 12, 2011, [https://port70.net/~nsz/c/c11/n1570.pdf](https://port70.net/~nsz/c/c11/n1570.pdf).
<!--ID: 1732843837987-->
END%%
%%ANKI
Basic
What does the `memcpy` function do?
Back: Copies a specified number of bytes from one object to another.
Reference: “ISO: Programming Languages - C,” April 12, 2011, [https://port70.net/~nsz/c/c11/n1570.pdf](https://port70.net/~nsz/c/c11/n1570.pdf).
<!--ID: 1732843837989-->
END%%
%%ANKI
Basic
Disregarding out of bounds errors, when does `memcpy` invoke undefined behavior?
Back: When copying occurs between objects that overlap in memory.
Reference: “ISO: Programming Languages - C,” April 12, 2011, [https://port70.net/~nsz/c/c11/n1570.pdf](https://port70.net/~nsz/c/c11/n1570.pdf).
<!--ID: 1732843837990-->
END%%
%%ANKI
Basic
What does the first argument of `memcpy` refer to?
Back: The destination address bytes are copied to.
Reference: “ISO: Programming Languages - C,” April 12, 2011, [https://port70.net/~nsz/c/c11/n1570.pdf](https://port70.net/~nsz/c/c11/n1570.pdf).
<!--ID: 1732843837991-->
END%%
%%ANKI
Basic
What does the second argument of `memcpy` refer to?
Back: The source address bytes are copied from.
Reference: “ISO: Programming Languages - C,” April 12, 2011, [https://port70.net/~nsz/c/c11/n1570.pdf](https://port70.net/~nsz/c/c11/n1570.pdf).
<!--ID: 1732843837993-->
END%%
%%ANKI
Basic
What does the third argument of `memcpy` refer to?
Back: The number of bytes to copy from the source address.
Reference: “ISO: Programming Languages - C,” April 12, 2011, [https://port70.net/~nsz/c/c11/n1570.pdf](https://port70.net/~nsz/c/c11/n1570.pdf).
<!--ID: 1732843837994-->
END%%
%%ANKI
Basic
Which of `memcpy` or `memmove` is faster?
Back: `memcpy`
Reference: “ISO: Programming Languages - C,” April 12, 2011, [https://port70.net/~nsz/c/c11/n1570.pdf](https://port70.net/~nsz/c/c11/n1570.pdf).
<!--ID: 1732843837995-->
END%%
%%ANKI
Basic
*Why* is `memmove` slower than `memcpy`?
Back: It's implemented as if copying first into a temporary array that does not overlap the arguments in memory.
Reference: “ISO: Programming Languages - C,” April 12, 2011, [https://port70.net/~nsz/c/c11/n1570.pdf](https://port70.net/~nsz/c/c11/n1570.pdf).
<!--ID: 1732843837996-->
END%%
%%ANKI
Basic
When should you prefer using `memcpy` instead of `memmove`?
Back: When the copying occurs between objects that do not overlap in memory.
Reference: “ISO: Programming Languages - C,” April 12, 2011, [https://port70.net/~nsz/c/c11/n1570.pdf](https://port70.net/~nsz/c/c11/n1570.pdf).
<!--ID: 1732843837997-->
END%%
%%ANKI
Basic
Which standard header library defines `memcpy`?
Back: `<string.h>`
Reference: “ISO: Programming Languages - C,” April 12, 2011, [https://port70.net/~nsz/c/c11/n1570.pdf](https://port70.net/~nsz/c/c11/n1570.pdf).
<!--ID: 1732843837998-->
END%%
%%ANKI
Basic
What is the function prototype of `memmove`?
Back:
```c
void* memmove(void* s1, const void* s2, size_t n);
```
Reference: “ISO: Programming Languages - C,” April 12, 2011, [https://port70.net/~nsz/c/c11/n1570.pdf](https://port70.net/~nsz/c/c11/n1570.pdf).
<!--ID: 1732843837999-->
END%%
%%ANKI
Basic
What does the first argument of `memmove` refer to?
Back: The destination address bytes are copied to.
Reference: “ISO: Programming Languages - C,” April 12, 2011, [https://port70.net/~nsz/c/c11/n1570.pdf](https://port70.net/~nsz/c/c11/n1570.pdf).
<!--ID: 1732843838000-->
END%%
%%ANKI
Basic
What does the second argument of `memmove` refer to?
Back: The source address bytes are copied from.
Reference: “ISO: Programming Languages - C,” April 12, 2011, [https://port70.net/~nsz/c/c11/n1570.pdf](https://port70.net/~nsz/c/c11/n1570.pdf).
<!--ID: 1732843838001-->
END%%
%%ANKI
Basic
What does the third argument of `memmove` refer to?
Back: The number of bytes to copy from the source address.
Reference: “ISO: Programming Languages - C,” April 12, 2011, [https://port70.net/~nsz/c/c11/n1570.pdf](https://port70.net/~nsz/c/c11/n1570.pdf).
<!--ID: 1732843838002-->
END%%
%%ANKI
Basic
Disregarding out of bounds errors, when does `memmove` invoke undefined behavior?
Back: N/A.
Reference: “ISO: Programming Languages - C,” April 12, 2011, [https://port70.net/~nsz/c/c11/n1570.pdf](https://port70.net/~nsz/c/c11/n1570.pdf).
<!--ID: 1732843838003-->
END%%
%%ANKI
Basic
When should you prefer using `memmove` instead of `memcopy`?
Back: When the copying occurs between objects that overlap in memory.
Reference: “ISO: Programming Languages - C,” April 12, 2011, [https://port70.net/~nsz/c/c11/n1570.pdf](https://port70.net/~nsz/c/c11/n1570.pdf).
<!--ID: 1732843838004-->
END%%
%%ANKI
Basic
Which standard header library defines `memmove`?
Back: `<string.h>`
Reference: “ISO: Programming Languages - C,” April 12, 2011, [https://port70.net/~nsz/c/c11/n1570.pdf](https://port70.net/~nsz/c/c11/n1570.pdf).
<!--ID: 1732843838005-->
END%%
%%ANKI
Basic
What does the `memmove` function do?
Back: Copies a specified number of bytes from one object to another.
Reference: “ISO: Programming Languages - C,” April 12, 2011, [https://port70.net/~nsz/c/c11/n1570.pdf](https://port70.net/~nsz/c/c11/n1570.pdf).
<!--ID: 1732843838006-->
END%%
## Bibliography
* Arnold D. Robbins, “GAWK: Effective AWK Programming,” October 2023, [https://www.gnu.org/software/gawk/manual/gawk.pdf](https://www.gnu.org/software/gawk/manual/gawk.pdf).
* Brian W. Kernighan and Dennis M. Ritchie, *The C Programming Language*, 2nd ed (Englewood Cliffs, N.J: Prentice Hall, 1988).
* Bryant, Randal E., and David O'Hallaron. *Computer Systems: A Programmer's Perspective*. Third edition, Global edition. Always Learning. Pearson, 2016.
* “ISO: Programming Languages - C,” April 12, 2011, [https://port70.net/~nsz/c/c11/n1570.pdf](https://port70.net/~nsz/c/c11/n1570.pdf).
* Jens Gustedt, _Modern C_ (Shelter Island, NY: Manning Publications Co, 2020).
* Mendel Cooper, “Advanced Bash-Scripting Guide,” n.d., 916.
* “Printf,” in *Wikipedia*, January 18, 2024, [https://en.wikipedia.org/w/index.php?title=Printf&oldid=1196716962](https://en.wikipedia.org/w/index.php?title=Printf&oldid=1196716962).

2
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@ -309,7 +309,7 @@ Let $Q$ be a set. If there exists exactly one $c$ such that $a(S) \leq c \leq a(
Cloze
Let $Q$ be a set. The {exhaustion} property of area states:
if there exists {exactly one} $c \in \mathbb{R}$ such that {$a(S) \leq c \leq a(T)$} for all {step regions} $S$ and $T$ satisfying {$S \subseteq Q \subseteq T$}, then {$Q \in \mathscr{M}$} and {$a(Q) = c$}.
If there exists {exactly one} $c \in \mathbb{R}$ such that {$a(S) \leq c \leq a(T)$} for all {step regions} $S$ and $T$ satisfying {$S \subseteq Q \subseteq T$}, then {$Q \in \mathscr{M}$} and {$a(Q) = c$}.
Reference: Tom M. Apostol, _Calculus, Vol. 1: One-Variable Calculus, with an Introduction to Linear Algebra_, 2nd ed. (New York: Wiley, 1980).
<!--ID: 1732381333427-->
END%%

2
notes/lambda-calculus/alpha-conversion.md
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@ -139,7 +139,7 @@ END%%
%%ANKI
Basic
Is the following identity true? $$\lambda x y. x(xy) \equiv \lambda u v. u(uv))$$
Is the following identity true? $$\lambda x y. x(xy) \equiv \lambda u v. u(uv)$$
Back: No.
Reference: Hindley, J Roger, and Jonathan P Seldin. “Lambda-Calculus and Combinators, an Introduction,” n.d. [https://www.cin.ufpe.br/~djo/files/Lambda-Calculus%20and%20Combinators.pdf](https://www.cin.ufpe.br/~djo/files/Lambda-Calculus%20and%20Combinators.pdf).
<!--ID: 1717687744169-->