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How exactly does the callstack work?
...standing of how the low level operations of programming languages work and especially how they interact with the OS/CPU. I've probably read every answer in every stack/heap related thread here on Stack Overflow, and they are all brilliant. But there is still one thing that I didn't fully understand...
Is there any overhead to declaring a variable within a loop? (C++)
...0) { var = 4; } }
gcc -S 1.c
1.s:
_main:
pushl %ebp
movl %esp, %ebp
subl $24, %esp
movl $0, -16(%ebp)
jmp L2
L3:
movl $4, -12(%ebp)
L2:
cmpl $99, -16(%ebp)
jle L3
leave
ret
2.c
main() { while(int i < 100) { int var = 4; } }
gcc -S ...
What is the purpose of the EBP frame pointer register?
...ocal variable or an argument is at with a single constant offset. Although ESP's value changes over the course of execution, EBP remains the same making it possible to reach the same variable at the same offset (such as first parameter will always be at EBP+8 while ESP offsets can change significant...
从Sloodle看三维虚拟学习环境的发展趋势 - 资讯 - 清泛网 - 专注C/C++及内核技术
...的视频 ,这已经在技术上能够实现了 ,更进一步 ,能否使用摄像头自动实时捕获用户的头像使得用户替身更加真实 ? 另一方面 ,能否将虚拟环境、虚拟对象与真实学习活动相结合 ? 三维虚拟学习环境毕竟都是虚拟的 ,是一种辅助手...
Try-catch speeding up my code?
...le stores and the way the JIT compiler does register scheduling in the corresponding x86 code. The result is suboptimal code generation on the loads and stores of the locals.
For some reason unclear to all of us, the problematic code generation path is avoided when the JITter knows that the block i...
Difference between passing array and array pointer into function in C
... type derivation, then for each call to the function, the value of the corresponding
actual argument shall provide access to the first element of an array with at least as many
elements as specified by the size expression.
So, in short, any function parameter declared as T a[] or T a[N] is treated...
How does this milw0rm heap spraying exploit work?
...EA8331FC0B6A6A jmp 0x6a6a:0xbfc3183
00000017 03D4 add edx,esp
00000019 07 pop es
0000001A 67305CFF xor [si-0x1],bl
0000001E 98 cwde
0000001F BBD7FFA4FE mov ebx,0xfea4ffd7
00000024 9B wait
00000025 74AD j...
Is volatile expensive?
...R-133 Cookbook for Compiler Writers about the implementation of volatile, especially section "Interactions with Atomic Instructions" I assume that reading a volatile variable without updating it needs a LoadLoad or a LoadStore barrier. Further down the page I see that LoadLoad and LoadStore are eff...
GDB corrupted stack frame - How to debug?
...ff the stack. In 32-bit x86 code you just do:
(gdb) set $pc = *(void **)$esp
(gdb) set $esp = $esp + 4
With 64-bit x86 code you need
(gdb) set $pc = *(void **)$rsp
(gdb) set $rsp = $rsp + 8
Then, you should be able to do a bt and figure out where the code really is.
The other 1% of the time,...
Do sealed classes really offer performance Benefits?
... = new NormalClass();
00000000 push ebp
00000001 mov ebp,esp
00000003 sub esp,8
00000006 cmp dword ptr ds:[00585314h],0
0000000d je 00000014
0000000f call 70032C33
00000014 xor edx,edx
00000016 mov dword ptr [ebp-4],edx
0...