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articles/pointer.md: update

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tocariimaa 2025-02-11 01:16:42 -03:00
parent fefe7e1ef3
commit 323906de43
1 changed files with 4 additions and 3 deletions
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articles/pointer.md
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@ -6,7 +6,7 @@ Here, the pointer `str` has the value of 0xdecade, therefore pointing to the mem
that address (here a C string): that address (here a C string):
address | data address | data
----------------- ----------+-------
uint16_t *n ---> 0xdecadb | 0x27 uint16_t *n ---> 0xdecadb | 0x27
0xdecadc | 0x7f 0xdecadc | 0x7f
0xdecadd | 0xff 0xdecadd | 0xff
@ -17,6 +17,7 @@ char *str -----> 0xdecade | 'H'
0xdecae2 | 'o' 0xdecae2 | 'o'
char *end -----> 0xdecae3 | 0x00 char *end -----> 0xdecae3 | 0x00
0xdecae4 | 0x27 0xdecae4 | 0x27
----------+------
char c = *str; /* dereferencing, reading the first element */ char c = *str; /* dereferencing, reading the first element */
char c4 = *(str + 4); /* with pointer arithmetic we can access the 4th element, 'o' */ char c4 = *(str + 4); /* with pointer arithmetic we can access the 4th element, 'o' */
@ -56,5 +57,5 @@ process. On embedded systems (without a MMU), a null pointer may represent a val
## Function pointers ## Function pointers
Function pointers are more special. On most systems, just like a regular pointer, a function pointer is simply Function pointers are more special. On most systems, just like a regular pointer, a function pointer is simply
a memory address to the start of the function code. Formally in C, dereferencing a function pointer is undefined a memory address to the start of the function code. In some weird architectures like Itanium it is a pair of two addresses.
behavior. Formally in C, dereferencing a function pointer is undefined behavior.