gcc

问题 I am trying to write my own malloc implementation, following an online course. Issue I am facing is that i always get segmentation fault, and when i tried to debug it always point to printf statement, which is just a string. After further investigation i found the value for sbrk(0) always increase after printf gets called. I am not sure but i think my malloc implementation overwrites some memory space that printf might be using. But is it possible for printf to be there. The program works

问题 This is a particularized question from mingw32/bin/ld.exe ... undefined reference to [class] ... collect2.exe: error: ld returned 1 exit status There is a user-defined class inside MyClass.hpp: class MyClass { public: MyClass(const string& className); ~MyClass() {cout << "Destructor definition instead of g++ default one?";} ; ... and you try to construct an object out of it in the main file: #include "MyClass.hpp" //in the same directory ... int main() { ... MyClass myClassObj = MyClass

问题 This is a particularized question from mingw32/bin/ld.exe ... undefined reference to [class] ... collect2.exe: error: ld returned 1 exit status There is a user-defined class inside MyClass.hpp: class MyClass { public: MyClass(const string& className); ~MyClass() {cout << "Destructor definition instead of g++ default one?";} ; ... and you try to construct an object out of it in the main file: #include "MyClass.hpp" //in the same directory ... int main() { ... MyClass myClassObj = MyClass

问题 Is there a way to perform compile-time function execution in C? With GCC? I've only seen this available using constexpr in C++. 回答1: As long as there are only constants involved in an expression, it will get calculated at compile-time. C++ constexpr is mostly a type safe way of doing so without involving macros. In C, there are only macros. For example: #define CIRCLE_AREA(r) (int32_t)( (double)(r) * (double)(r) * M_PI ) int32_t area = CIRCLE_AREA(5); performs all calculations at compile-time

问题 I am trying to compile a linux c++ source code on Windows 7 Cygwin and getting following error: $ make getconf: Unrecognized variable `LFS_CFLAGS' gcc -O3 -Wall -Wextra -g -DVERSION='"v1.1.0"' -c src/main.c -o src/main.o src/main.c:10:25: schwerwiegender Fehler: sys/syscall.h: No such file or directory #include <sys/syscall.h> ^ Kompilierung beendet. Makefile:48: recipe for target 'src/main.o' failed make: *** [src/main.o] Error 1 I googled this but hadn't any success. Any ideas? 回答1: syscall

问题 I am trying to compile a linux c++ source code on Windows 7 Cygwin and getting following error: $ make getconf: Unrecognized variable `LFS_CFLAGS' gcc -O3 -Wall -Wextra -g -DVERSION='"v1.1.0"' -c src/main.c -o src/main.o src/main.c:10:25: schwerwiegender Fehler: sys/syscall.h: No such file or directory #include <sys/syscall.h> ^ Kompilierung beendet. Makefile:48: recipe for target 'src/main.o' failed make: *** [src/main.o] Error 1 I googled this but hadn't any success. Any ideas? 回答1: syscall

问题 all, I was compiling a C program with OpenMP. It's my first time to use makefile. When excuting "make", the gcc reports the error make: * No rule to make target omp.h', needed by smooth.o'. Stop. However the omp.h is in the /usr/lib/gcc/i686-linux-gnu/4.6/include/omp.h , I am wondering how to fix it. Could anyone help me? Thank you. CC=gcc CFLAGS = -fopenmp all: smooth smooth: smooth.o ompsooth.o $(CC) $(CFLAGS) -o smooth smooth.o ompsmooth.o ompsmooth.o: ompsmooth.c assert.h stdio.h stdlib.h

问题 In chapter 3 of Programming: Principles and Practice using C++ (sixth printing), Stroustrup states (p.68): "Note that sqrt() is not defined for an int " . Here is a simple C++ program based on that chapter: #include "std_lib_facilities.h" int main() { int n = 3; cout << "Square root of n == " << sqrt(n) << "\n"; } Given the quote above, I would expect the process of compiling or running this program to fail in some way. To my surprise, compiling it (with g++ (GCC) 4.2.1) and running it

问题 There are two ways of implementation of accumulation in sse intrinsic. But one of them gets the wrong result. #include <smmintrin.h> int main(int argc, const char * argv[]) { int32_t A[4] = {10, 20, 30, 40}; int32_t B[8] = {-1, 2, -3, -4, -5, -6, -7, -8}; int32_t C[4] = {0, 0, 0, 0}; int32_t D[4] = {0, 0, 0, 0}; __m128i lv = _mm_load_si128((__m128i *)A); __m128i rv = _mm_load_si128((__m128i *)B); // way 1 unexpected rv += lv; _mm_store_si128((__m128i *)C, rv); // way 2 expected rv = _mm_load

问题 There are two ways of implementation of accumulation in sse intrinsic. But one of them gets the wrong result. #include <smmintrin.h> int main(int argc, const char * argv[]) { int32_t A[4] = {10, 20, 30, 40}; int32_t B[8] = {-1, 2, -3, -4, -5, -6, -7, -8}; int32_t C[4] = {0, 0, 0, 0}; int32_t D[4] = {0, 0, 0, 0}; __m128i lv = _mm_load_si128((__m128i *)A); __m128i rv = _mm_load_si128((__m128i *)B); // way 1 unexpected rv += lv; _mm_store_si128((__m128i *)C, rv); // way 2 expected rv = _mm_load