How Can I Get See A Memory Map For An Executable

How Can I Get See A Memory Map For An Executable

[Steven Woody]

i want to check in my C++ program, what variable is allocated in where. is
there such a tool?

another relative question is, where the 'new' operator get memory from? the
global heap? does it same with what 'malloc' get from?

thanks.

-- 
steven woody (id: narke)

Re: How Can I Get See A Memory Map For An Executable

[Ian Lance Taylor]

Steven Woody <narkewoody@gmail.com> writes:

> i want to check in my C++ program, what variable is allocated in where. is
> there such a tool?

I don't know if it will much, but the GNU linker supports a -Map
option.  See the documentation.  You can also use nm or objdump -t or
readelf -s to see where symbols are in the fully linked executable.

> another relative question is, where the 'new' operator get memory from? the
> global heap? does it same with what 'malloc' get from?

In general, the answers are yes and yes.

Ian

Re: How Can I Get See A Memory Map For An Executable

[Steven Woody]

Ian Lance Taylor <ian@airs.com> writes:

> Steven Woody <narkewoody@gmail.com> writes:
>
>> i want to check in my C++ program, what variable is allocated in where. is
>> there such a tool?
>
> I don't know if it will much, but the GNU linker supports a -Map
> option.  See the documentation.  You can also use nm or objdump -t or
> readelf -s to see where symbols are in the fully linked executable.

thank you, but neither of these commands can clearly print size of each segment
( such as heap, bss, text). but, thanks anyway.

>
>> another relative question is, where the 'new' operator get memory from? the
>> global heap? does it same with what 'malloc' get from?
>
> In general, the answers are yes and yes.

thanks.  could you also tell me what's the difference between local heap and
global heap, i can not recall where i heard the the terms.


>
> Ian
>

-- 
steven woody (id: narke)

John McFarland: Hey, what are you guys doing?
Alex: Get the fuck out and don't come back! Some heavy shit's going down! 

	- Elephant (2003)

Re: How Can I Get See A Memory Map For An Executable

[Ian Lance Taylor]

Steven Woody <narkewoody@gmail.com> writes:

> thank you, but neither of these commands can clearly print size of each segment
> ( such as heap, bss, text). but, thanks anyway.

The size program will print the size of the text and bss sections.

The size of the heap program is determined at runtime.  I do not know
of any program which can determine it statically.

> >> another relative question is, where the 'new' operator get memory from? the
> >> global heap? does it same with what 'malloc' get from?
> >
> > In general, the answers are yes and yes.
> 
> thanks.  could you also tell me what's the difference between local heap and
> global heap, i can not recall where i heard the the terms.

I don't know where you heard the terms either.  On a typical Unix (or
GNU/Linux) system, programs have only one heap.

Ian

Re: How Can I Get See A Memory Map For An Executable

[Steven Woody]

Ian Lance Taylor <ian@airs.com> writes:

> Steven Woody <narkewoody@gmail.com> writes:
>
>> thank you, but neither of these commands can clearly print size of each segment
>> ( such as heap, bss, text). but, thanks anyway.
>
> The size program will print the size of the text and bss sections.
>
> The size of the heap program is determined at runtime.  I do not know
> of any program which can determine it statically.

if the heap is not determined statically, how much in size at startup the
program get the big pool to allocate for each 'new' or 'malloc' calling?

>
>> >> another relative question is, where the 'new' operator get memory from? the
>> >> global heap? does it same with what 'malloc' get from?
>> >
>> > In general, the answers are yes and yes.
>> 
>> thanks.  could you also tell me what's the difference between local heap and
>> global heap, i can not recall where i heard the the terms.
>
> I don't know where you heard the terms either.  On a typical Unix (or
> GNU/Linux) system, programs have only one heap.

at least, for embedded system, the programmer has to specify how much size for
each kind of heap, NEAR heap, FAR heap, etc.  for Linux, i've not got the
picture. 

>
> Ian
>

-- 
steven woody (id: narke)

Re: How Can I Get See A Memory Map For An Executable

[Ian Lance Taylor]

Steven Woody <narkewoody@gmail.com> writes:

> >> thank you, but neither of these commands can clearly print size of each segment
> >> ( such as heap, bss, text). but, thanks anyway.
> >
> > The size program will print the size of the text and bss sections.
> >
> > The size of the heap program is determined at runtime.  I do not know
> > of any program which can determine it statically.
> 
> if the heap is not determined statically, how much in size at startup the
> program get the big pool to allocate for each 'new' or 'malloc' calling?

These questions are no longer about gcc, if indeed they ever were.
They are basic Unix questions.  Please take further questions along
these lines to some other mailing list or news group.  Thanks.

Unix systems use virtual memory.  A large chunk of the address space
is available for the heap--all the address space between the end of
the program and the stack.  Any program can theoretically use all of
that space.

Unix programs do not request a certain amount of space when they
start.  They simply request more space as they need it, using the
brk() and sbrk() functions.

> > I don't know where you heard the terms either.  On a typical Unix (or
> > GNU/Linux) system, programs have only one heap.
> 
> at least, for embedded system, the programmer has to specify how much size for
> each kind of heap, NEAR heap, FAR heap, etc.  for Linux, i've not got the
> picture. 

On GNU/Linux there is only one heap, and it is limited primarily by
the size of the address space.

Ian

Re: How Can I Get See A Memory Map For An Executable

[Steven Woody]

Ian Lance Taylor <ian@airs.com> writes:

> Steven Woody <narkewoody@gmail.com> writes:
>
>> >> thank you, but neither of these commands can clearly print size of each segment
>> >> ( such as heap, bss, text). but, thanks anyway.
>> >
>> > The size program will print the size of the text and bss sections.
>> >
>> > The size of the heap program is determined at runtime.  I do not know
>> > of any program which can determine it statically.
>> 
>> if the heap is not determined statically, how much in size at startup the
>> program get the big pool to allocate for each 'new' or 'malloc' calling?
>
> These questions are no longer about gcc, if indeed they ever were.
> They are basic Unix questions.  Please take further questions along
> these lines to some other mailing list or news group.  Thanks.
>
> Unix systems use virtual memory.  A large chunk of the address space
> is available for the heap--all the address space between the end of
> the program and the stack.  Any program can theoretically use all of
> that space.
>
> Unix programs do not request a certain amount of space when they
> start.  They simply request more space as they need it, using the
> brk() and sbrk() functions.
>
>> > I don't know where you heard the terms either.  On a typical Unix (or
>> > GNU/Linux) system, programs have only one heap.
>> 
>> at least, for embedded system, the programmer has to specify how much size for
>> each kind of heap, NEAR heap, FAR heap, etc.  for Linux, i've not got the
>> picture. 
>
> On GNU/Linux there is only one heap, and it is limited primarily by
> the size of the address space.

thanks for the answer.

>
> Ian
>

-- 
steven woody (id: narke)

Re: How Can I Get See A Memory Map For An Executable

[Mike Stump]

On Nov 12, 2005, at 11:38 PM, Steven Woody wrote:
> i want to check in my C++ program, what variable is allocated in  
> where. is
> there such a tool?

gdb is useful for debugging.

> another relative question is, where the 'new' operator get memory  
> from?

malloc.

> the global heap? does it same with what 'malloc' get from?

Yes.