Alloca is a function to allocate dynamically memory on the Stack in C. Such memory will be automatically deallocated when leaving the function.
Questions tagged [alloca]
87 questions
1
vote
3 answers
Please give me the clarity on this
num1=0
Stored_num=23
def input_num():
num1=int(input('Enter the number again: '))
while num1!=stored_num:
input_num()
else:
print('Congrats ! The entered number mathched the stored number')
The code above is not accepting the else…
Rajan Deshmukh
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- 2
1
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1 answer
Trying to understand the Assembly implementation of the alloca() function on x86
I am very new to assembly and I am currently reading a book called Reverse Engineering for Beginners and I got to the part that talks about memory allocation on the stack.
I understand (I think) the concept of stack allocation but in the example…
Ronen
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2 answers
strdupa() implementation for Visual C
I am trying to port a C (not C++) program from GCC to Visual Studio.
The GCC specific function strdupa() is widely used in this program.
Is there any way to implement this function for Visual C.
PS. I understand that it uses alloca() and it is…
Sandro
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2 answers
How to replace alloca in an implementation of execvp()?
Take a look at the NetBSD implementation of execvp here:
http://cvsweb.netbsd.se/cgi-bin/bsdweb.cgi/src/lib/libc/gen/execvp.c?rev=1.30.16.2;content-type=text%2Fplain
Note the comment at line 130, in the special case for handling ENOEXEC:
/*
* we…
amoe
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2 answers
Declaring memory on stack overwrites previously declared memory
How can I allocate memory on the stack and have it point to different memory addresses so I can use it later? For example. this code:
for (int i = 0; i < 5; i++) {
int nums[5];
nums[0] = 1;
printf("%p\n", &nums[0]);
}
Will print out the…
Aamir
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1 answer
How can I emulate a stack frame in C++?
I am writing a container that uses alloca internally to allocate data on the stack. Risks of using alloca aside, assume that I must use it for the domain I am in (it's partly a learning exercise around alloca and partly to investigate possible…
OMGtechy
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4 answers
Allocate aligned memory on the stack like _alloca
The documentation for _alloca() says here:
The _alloca routine returns a void pointer to the allocated space,
which is guaranteed to be suitably aligned for storage of any type of
object.
However, here it says:
_alloca is required to be…
Serge Rogatch
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1
vote
1 answer
symbol lookup error: undefined symbol: _alloca
I'm building a shared object (.so) that internally makes use of a function _alloca() (defined in malloc.h). This .so compiles smoothly. But as soon as I call a function that makes use of _alloca(), my application crashes whith a console…
Elmi
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1 answer
alloca inside compound statement
is it possible to use alloca inside compound statement?
Example:
typedef struct
{
size_t len;
char* data;
} string_t;
#define str_to_cstr(str) \
({ \
char* v = alloca(str.len + 1); \
v[len] = 0; \
memcpy(v, str.data, str.len);…
user939407
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1
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4 answers
C usage of malloc inside a function
I have the following function:
char * decrypt(const char *p, int key) {
char *tmp = malloc(strlen(p) + 1);
for (int i = 0; p[i] != '\0'; i++) {
if (p[i] >= 'A' && p[i] <= 'Z') {
if (key <= p[i] - 'A')
tmp[i] = p[i] - key;
…
user3340372
1
vote
2 answers
Wrap alloca function in C
Is it possible to wrap the C function alloca into "another"? (only macros of course)
Something like:
#define my_alloca(size) \
({ \
…
Marco
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1 answer
Intended usage of alloca/memset in LLVM
When allocating space on the stack using alloca(), is it necessary to clear the memory or is it guaranteed to contain only zeros?
I came up with the following LLVM code. Although it compiles, it leads to a core dump.
In the code I was trying to…
user3267915
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1
vote
1 answer
alloca and ObjectiveC Garbage Collector
In an objective C project with GC enabled, I am allocating an array of variable size on the stack like this:
MaValue *myStack = alloca((sizeof(id) * someLength));
(The reason why I want to do this is not important:)
Then, within a loop, I push and…
Christoph
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1
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1 answer
alloca() of a templated array of types: how to do this?
I have a smart pointer type, and would like to construct an object that takes a pointer of that type and a count (dynamically calculated at runtime) and allocates enough memory from the stack to hold that many instances of the object the smart…
moonshadow
- 86,889
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0
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8 answers
Resizing dynamic stack allocations in C++
I'm writing a small ray tracer using bounding volume hierarchies to accelerate ray tracing.
Long story short, I have a binary tree and I might need to visit multiple leafs.
Current I have a node with two children left and right, then during travel()…
jonasfj
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