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134 lines
3.6 KiB
Plaintext
134 lines
3.6 KiB
Plaintext
Section 7: Foundation of Processes (Part A):
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--------------------------------------------
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-> The Program Stack:
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++++++++++++++++++
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+-----------------------+
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| Bottom of stack |
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+-----------------------+
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| stack | <- Fixed size*1
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+-----------------------+
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| (Unallocated) |
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+-----------------------+
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| Heap (Dynamic Data)|
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+-----------------------+
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| Static Data |
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+-----------------------+
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| Literals | <- Like String literals
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+-----------------------+
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| Instructions | <- This section contains the code (asm code)
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+-----------------------+
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| Top of stack |
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+-----------------------+
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*1
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By fixed size we mean that when we compile the program
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the size of the stack is predetermined. We can increment
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the size of the stack but the size is fixed once compiled.
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Fun fact: NASA use only stack memory for their embedded system
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while writing code for their rovers.
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-> What is a Call stack?
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+++++++++++++++++++++
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+--------+
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| main |
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+--------+
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| square |-----/
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+--------+ |
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\
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Frame
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+----------------+
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| parameters |
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| return address|
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| locals | * Each Call stack has one section called as frame
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| exceptions | which contains the information for certain operations.
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| | These operations are self explainatory as written.
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+----------------+
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-> Navigate the Call Stack with Backtrace:
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++++++++++++++++++++++++++++++++++++++
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* To know about the call stack of functions, we can use...
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Command:
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(gdb)bt
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This shows what are the function calls to trace back to the
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beginning function, which is "main" in C and C++.
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* To know about the arguments and the value passed to the current
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function in which we are present, we can use...
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Command:
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(gdb)info args
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* To know about the local variables of the current functions context,
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we can use...
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Command:
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(gdb)info locals
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* To know about the frame section of the function call stack, we can use:
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Command:
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(gdb)info frame
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* To get us out of the function that we are currently in without terminating
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the execution of the program.
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Command:
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(gdb)finish
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or
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(gdb)fin
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* To move up in the stack, i.e. moving to the context of the calling function
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, we can use....
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Command:
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(gdb)up
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* To move up down the stack, i.e. moving to the context of the callee function
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, we can use...
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Command
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(gdb)down
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* Segmentation fault:
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~~~~~~~~~~~~~~~~~~~
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It is the section of memory which the program is trying to access
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and it is out of bound.
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For this kind of error, we get signal from kernel SIGSEGV.
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* Memory leak:
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~~~~~~~~~~~~
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Failure to reclaim memory while our program runs.
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We can also use tools like valgrind to detect memory leak issue.
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Command:
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$valgrind ./<program>
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We can also use Address-sanitizers
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