All Questions
26 questions
-3
votes
3
answers
129
views
How does does compiler know the definition of pre defined function even before linker haven't linked object file and library file?
We know that definition of pre defined functions are in library files, and it is the job of linker to link that library code(which is already compiled) to our object file (which has been created after ...
2
votes
0
answers
240
views
reference to external function in disassembly code [duplicate]
I am trying to see everything in big picture regarding compilation and linking.
I have below simple function implemented in add_caller.c :
extern int add(int a, int b);
int
main(int argc, char **...
- 1,346
8
votes
3
answers
653
views
Global const optimization and symbol interposition
I was experimenting with gcc and clang to see if they can optimize
#define SCOPE static
SCOPE const struct wrap_ { const int x; } ptr = { 42 /*==0x2a*/ };
SCOPE struct wrap { const struct wrap_ *ptr; ...
- 60.3k
3
votes
3
answers
472
views
How does linker handle variables with different linkages?
In C and C++ we can manipulate a variable's linkage. There are three kinds of linkage: no linkage, internal linkage, and external linkage. My question is probably related to why these are called "...
- 3,990
2
votes
1
answer
111
views
Can const variables be modified from elsewhere not known at compile time
If const is a compile time construct, it would mean that only the compiler will ensure that for example if a variable is declared as const, this variable is read only and it is not attempted to be ...
- 4,061
1
vote
1
answer
512
views
What's the necessity of .bss section in an object file? [duplicate]
Wikipedia mentions that .bss section occupies no actual space in the object file, and I indeed find a .bss entry with size 0 in the objdump information. So the question is what's the necessity of such ...
- 69
4
votes
1
answer
2k
views
How does a linker work exactly (microcontroller context)?
I've been programming in C and C++ for quite a long time now, so I'm familiar with the linking process as a user: the preprocessor expands all prototypes and macros in each .c file which is then ...
- 1,002
2
votes
0
answers
549
views
static compilation and got, plt sections.
I am writing a toy elf loader for some small project. To test my loader, I have been compiling my app statically. However, I realized even after static compilation, my app still contains .got and .got....
- 9,476
0
votes
2
answers
170
views
How linker creates executable files and links C keywords
I have created 2 C programs in Ubuntu(Linux 2.6) as below
1.c
----
main()
{
}
2.c
----
#include<stdio.h>
main()
{
int a[500];
float f[1000];
double d[100000];
int i = 0;
for(i = 0;i < 10000;...
- 9
0
votes
2
answers
443
views
How a pointer initialization C statement in global space gets its assigned value during compile/link time?
The background of this question is to understand how the compiler/linker deals with the pointers when it is initialized in global space.
For e.g.
#include <stdio.h>
int a = 8;
int *p = &a;...
- 51
1
vote
1
answer
1k
views
Relocating functions during run time - gcc
I'm working with 2 memories on my device, DDR and SRAM. The device is running a pre-OS code written in C and ARM.
I would like to conduct a DDR calibration, for that I need to copy a few functions to ...
- 745
9
votes
3
answers
3k
views
Why does inserting characters into an executable binary file cause it to "break"?
Why does inserting characters into an executable binary file cause it to "break" ?
And, is there any way to add characters without breaking the compiled program?
Background
I've known for a ...
- 1,426
3
votes
1
answer
702
views
How are variable and function references resolved (Linker & Compiler)? [closed]
I was reading this on SO when I actually started to wonder how the linker resolved especially adresses of symbols in an object file and how it would be organized inside the executable file outputted ...
- 1,323
32
votes
4
answers
21k
views
how do compilers assign memory addresses to variables?
I teach a course where students get to ask questions about programming (!): I got this question:
Why does the machine choose were variables go in memory? Can we tell
it where to store a variable?
...
- 20.2k
4
votes
2
answers
3k
views
How does the compiler know about the instruction set of my CPU? [closed]
I've read that
The compiler converts code written in a human-readable programming language into a
machine code representation which is understood by your processor.
How does the compiler know ...
- 169