Hi guys,
Consider the following piece of code:
func()
{
if(x==0) {
int arr[50];
/* do something */
}
else {
int arr2[100];
/* do something */
}
}
I wanted to know, if the space of arr[50 is allocated only when the
condition "x==0" is
true or the space is allocated when the function "func" is called.
I am working on an m68k implementation where the local varialbles are
allocated
on stack. I would be really grateful if anyone can provide me an
answer for an m68k
implementation.
thanks a lot for any help in advance ...
16  1566  ju**********@ya hoo.co.in wrote: Hi guys,
Consider the following piece of code:
func()
{
if(x==0) {
int arr[50];
/* do something */
}
else {
int arr2[100];
/* do something */
}
}
I wanted to know, if the space of arr[50 is allocated only when the
condition "x==0" is
true or the space is allocated when the function "func" is called.
I am working on an m68k implementation where the local varialbles are
allocated
on stack. I would be really grateful if anyone can provide me an
answer for an m68k
The answer would be compiler dependant, compiler flags dependant, and
code dependant. Some code , depending on the optimizations/etc. might be
reordered to play things out very differently than just some very
slightly different code.
Your best bet is to peek at the assembly(if available - gcc -S for gcc)
generated for the exact code you have compiled with the options you'll
be using in "production ". ju**********@ya hoo.co.in posted: Hi guys,
Consider the following piece of code:
func()
{
if(x==0) {
int arr[50];
/* do something */
}
else {
int arr2[100];
/* do something */
}
}
I wanted to know, if the space of arr[50 is allocated only when the
condition "x==0" is
true or the space is allocated when the function "func" is called.
I am working on an m68k implementation where the local varialbles are
allocated
on stack. I would be really grateful if anyone can provide me an
answer for an m68k
implementation.
thanks a lot for any help in advance ...
You could use an anonymous union. (Please correct me if they're not
Standard C).
union {
int arr[50];
int arr2[100];
};
--
Frederick Gotham
Nils O. Selåsdal wrote: ju**********@ya hoo.co.in wrote: Hi guys,
Consider the following piece of code:
func()
{
if(x==0) {
int arr[50];
/* do something */
}
else {
int arr2[100];
/* do something */
}
}
I wanted to know, if the space of arr[50 is allocated only when the
condition "x==0" is
true or the space is allocated when the function "func" is called.
I am working on an m68k implementation where the local varialbles are
allocated
on stack. I would be really grateful if anyone can provide me an
answer for an m68k
The answer would be compiler dependant, compiler flags dependant, and
code dependant. Some code , depending on the optimizations/etc. might be
reordered to play things out very differently than just some very
slightly different code.
Please correct me if i'm wrong.
Memory will be allocated for both arrays since it happens at
compilation time.
Here malloc comes into picture. It 'll do it at run time.
Once again i'm telling it's only my understanding. If wrong correct me.
Your best bet is to peek at the assembly(if available - gcc -S for gcc)
generated for the exact code you have compiled with the options you'll
be using in "production ".
On 26 Jun 2006 01:38:56 -0700, "ju**********@y ahoo.co.in"
<ju**********@y ahoo.co.in> wrote: Hi guys,
Consider the following piece of code:
func()
{
if(x==0) {
int arr[50];
/* do something */
}
else {
int arr2[100];
/* do something */
}
}
I wanted to know, if the space of arr[50 is allocated only when the
condition "x==0" is
true or the space is allocated when the function "func" is called.
I am working on an m68k implementation where the local varialbles are
allocated
on stack. I would be really grateful if anyone can provide me an
answer for an m68k
implementation.
In the context of this newsgroup, you don't know and should not care
when the allocation takes place. You must write code as if it took
place at the beginning of the block. For your particular problem, I
suggest you post on comp.arch.embed ded, and provide more detail about
the implementation you're using.
--
Al Balmer
Sun City, AZ
On Mon, 26 Jun 2006 13:36:56 GMT, Frederick Gotham
<fg*******@SPAM .com> wrote in comp.lang.c: ju**********@ya hoo.co.in posted:
Hi guys,
Consider the following piece of code:
func()
{
if(x==0) {
int arr[50];
/* do something */
}
else {
int arr2[100];
/* do something */
}
}
I wanted to know, if the space of arr[50 is allocated only when the
condition "x==0" is
true or the space is allocated when the function "func" is called.
I am working on an m68k implementation where the local varialbles are
allocated
on stack. I would be really grateful if anyone can provide me an
answer for an m68k
implementation.
thanks a lot for any help in advance ...
You could use an anonymous union. (Please correct me if they're not
Standard C).
They are not.
union {
int arr[50];
int arr2[100];
};
But you could define the union with a name:
union
{
int arr [50];
int arr2 [100];
} u;
--
Jack Klein
Home: http://JK-Technology.Com
FAQs for
comp.lang.c http://c-faq.com/
comp.lang.c++ http://www.parashift.com/c++-faq-lite/
alt.comp.lang.l earn.c-c++ http://www.contrib.andrew.cmu.edu/~a...FAQ-acllc.html
deepak wrote: Please correct me if i'm wrong.
Memory will be allocated for both arrays since it happens at
compilation time.
Here malloc comes into picture. It 'll do it at run time.
Once again i'm telling it's only my understanding. If wrong correct me.
This is where it pays to actually earn your post-secondary degree...
No, first off there is no runtime call to malloc.
Second, the implementation is free to either allocate enough memory to
hold the largest of the two (note that you can't access both
simultaneously) or allocate it as required.
By allocate I mean "make available". That may be a call to malloc
(likely it won't be) or a call to alloca() or just subtract the stack
pointer or .... .... ... it's not predefined. Recent releases of GCC
[by that I mean 3.x series and up] will analyze the function and
allocate stack in the preamble. But that is just how GCC chooses to do
it.
Tom
On 26 Jun 2006 07:48:31 -0700, "deepak" <de*********@gm ail.com> wrote
in comp.lang.c:
Nils O. Selåsdal wrote: ju**********@ya hoo.co.in wrote: Hi guys,
Consider the following piece of code:
func()
{
if(x==0) {
int arr[50];
/* do something */
}
else {
int arr2[100];
/* do something */
}
}
I wanted to know, if the space of arr[50 is allocated only when the
condition "x==0" is
true or the space is allocated when the function "func" is called.
I am working on an m68k implementation where the local varialbles are
allocated
on stack. I would be really grateful if anyone can provide me an
answer for an m68k
The answer would be compiler dependant, compiler flags dependant, and
code dependant. Some code , depending on the optimizations/etc. might be
reordered to play things out very differently than just some very
slightly different code.
Please correct me if i'm wrong.
Consider yourself corrected.
Memory will be allocated for both arrays since it happens at
compilation time.
That is true for objects with static storage duration, specifically
all objects defined at file scope or with the 'static' keyword.
Automatic objects do not need to be allocated until the block
containing their definition is entered.
Here malloc comes into picture. It 'll do it at run time.
Once again i'm telling it's only my understanding. If wrong correct me.
Your best bet is to peek at the assembly(if available - gcc -S for gcc)
generated for the exact code you have compiled with the options you'll
be using in "production ".
--
Jack Klein
Home: http://JK-Technology.Com
FAQs for
comp.lang.c http://c-faq.com/
comp.lang.c++ http://www.parashift.com/c++-faq-lite/
alt.comp.lang.l earn.c-c++ http://www.contrib.andrew.cmu.edu/~a...FAQ-acllc.html
"ju**********@y ahoo.co.in" <ju**********@y ahoo.co.in> writes: Hi guys,
Consider the following piece of code:
func()
{
if(x==0) {
int arr[50];
/* do something */
}
else {
int arr2[100];
/* do something */
}
}
I wanted to know, if the space of arr[50 is allocated only when the
condition "x==0" is
true or the space is allocated when the function "func" is called.
I am working on an m68k implementation where the local varialbles are
allocated
on stack. I would be really grateful if anyone can provide me an
answer for an m68k
implementation.
I'm interested in to why you would need to determine the difference even
assuming non portable code and the assertion that all locals are stack
based.
It cant be a memory thing since I assume x<>0 at some stage anyway so
you need to assume the stack space required for at leas 100 integers.
thanks a lot for any help in advance ...
--
Lint early. Lint often.
Tom St Denis wrote: deepak wrote: Please correct me if i'm wrong.
Memory will be allocated for both arrays since it happens at
compilation time.
Here malloc comes into picture. It 'll do it at run time.
Once again i'm telling it's only my understanding. If wrong correct me.
This is where it pays to actually earn your post-secondary degree...
No, first off there is no runtime call to malloc.
Second, the implementation is free to either allocate enough memory to
hold the largest of the two (note that you can't access both
simultaneously) or allocate it as required.
The implementation is also free to allocate both areas on the stack (if
such a thing is being used) at entry to the routine, or one on the
stack and the other dynamically, or...
Commonly these will be allocated on the stack as if they had been in a
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