assembly

问题 I've stored a 64-bit integer in the EDX:EAX register pair . How can I correctly negate the number? For example: 123456789123 → -123456789123 . 回答1: Ask a compiler for ideas: compile int64_t neg(int64_t a) { return -a; } in 32-bit mode. Of course, different ways of asking the compiler will have the starting value in memory, in the compiler's choice of registers, or already in EDX:EAX. See all three ways on the Godbolt compiler explorer, with asm output from gcc, clang, and MSVC (aka CL). There

问题 Since my main OS is linux and have project on visual studio, I decided to use online compilers to achieve it. I found this which was suggested by many. So here is my code: #include <iostream> using namespace std; int main(void) { float a = 1; float b = 20.2; float res = 0; float res1 = 0; _asm { FLD a FCOM b JA midi JMP modi midi: FST res JMP OUT modi: FST res1 JMP OUT } OUT: cout << "res = " << res << endl; cout << "res1 = " << res1 << endl; return 0; } My goal is simple, if a is greater

问题 I have the following snippet of inline assembly: procedure Foo; asm //..... @partialloop: shr rdx,1 //every instruction is 4 bytes lea r11,[rip + (7*4)+(@partial-@offset)] @offset: sub r11,rdx xor r8,r8 jmp r11 //do a partial loop @loop64: mov [rcx],rax @partial: mov [rcx+08H],rax //.... end; The compiler does not accept this syntax: E2105 Inline assembler syntax error Create use of offset , ptr or @@ does not help. What syntax do I need to use to make this compile? 回答1: Label addresses are

问题 I'm learning assembly language using x86 NASM. I wanted to write a simple recursive factorial function to which I am passing one parameter using EAX register. After that, I want to print my result on the screen but nothing happens. After sitting and staring on my computer I don't have any clue what is wrong with my code. Can you guys help newbie with this problem? I know that the prologue and epilogue of factorial funtion is not required due I'm not using stack but for me code is more

问题 On the website of GNU there is a simple example available which is supposed to demonstrate the problems appearing with non-atomic access. The example contains a small mistake, they have forgotten #include <unistd.h> : #include <signal.h> #include <stdio.h> #include <unistd.h> struct two_words { int a, b; } memory; static struct two_words zeros = { 0, 0 }, ones = { 1, 1 }; void handler(int signum) { printf ("%d,%d\n", memory.a, memory.b); alarm (1); } int main (void) { signal (SIGALRM, handler

问题 On the website of GNU there is a simple example available which is supposed to demonstrate the problems appearing with non-atomic access. The example contains a small mistake, they have forgotten #include <unistd.h> : #include <signal.h> #include <stdio.h> #include <unistd.h> struct two_words { int a, b; } memory; static struct two_words zeros = { 0, 0 }, ones = { 1, 1 }; void handler(int signum) { printf ("%d,%d\n", memory.a, memory.b); alarm (1); } int main (void) { signal (SIGALRM, handler

问题 On the website of GNU there is a simple example available which is supposed to demonstrate the problems appearing with non-atomic access. The example contains a small mistake, they have forgotten #include <unistd.h> : #include <signal.h> #include <stdio.h> #include <unistd.h> struct two_words { int a, b; } memory; static struct two_words zeros = { 0, 0 }, ones = { 1, 1 }; void handler(int signum) { printf ("%d,%d\n", memory.a, memory.b); alarm (1); } int main (void) { signal (SIGALRM, handler

问题 I'm trying to get better understanding of how assembly and machine code works. So I'm compiling this simple snipet with gcc : #include <stdio.h> int main(){ printf("Hello World!"); return 0; } But this includes the default library. I would like to output hello world without using printf but by inlining some assembly in the C file, and adding -nostdlib and -nodefaultlibs options to gcc. How can I do that ? I'm using Windows 10 and mingw-w64 with Intel core i7 6700 HQ (laptop processor). Can I

问题 I'm trying to get better understanding of how assembly and machine code works. So I'm compiling this simple snipet with gcc : #include <stdio.h> int main(){ printf("Hello World!"); return 0; } But this includes the default library. I would like to output hello world without using printf but by inlining some assembly in the C file, and adding -nostdlib and -nodefaultlibs options to gcc. How can I do that ? I'm using Windows 10 and mingw-w64 with Intel core i7 6700 HQ (laptop processor). Can I

问题 My program is supposed to ask for a single line of user input and then print out the number of characters in the string. As of now it is telling me there are 104 characters when I input hello followed by a segmentation fault. Here is my code: userInput: .asciz "\nEnter a string: " TemptRet: .word 10 inputBuffer: .skip 11 countMessage: .STRING "There are %d characters in: \"%s\".\n" .text .global main main: LDR R0, =courseStr BL puts countString: LDR R0, =userInput BL printf LDR R0, =TemptRet