g++

问题 Consider the following code: int x; int& f() { return x ? x : throw 0; } With gcc version 7.3.0 (Ubuntu 7.3.0-27ubuntu1~18.04) I get the following compilation error: cannot bind non-const lvalue reference of type ‘int&’ to an rvalue of type ‘int’ Note that this compiles just fine in clang. Here is (what I believe to be) the relevant statement from the standard: N4659 [8.16.2.1] (Conditional Operator): The second or the third operand (but not both) is a (possibly parenthesized) throw

问题 My team is writting code to be compiled for both Windows (using VS2015 ) and Android (using GCC 4.9 invoked by QtCreator ). We figured out that Android binaries had a problem with abs function. double a = 1.0; double b = 0.5; std::cout << abs( a - b ) << std::endl; std::cout << std::abs( a - b ) << std::endl; Displays: 1 0.5 This is a known issue, found this topic (among others): Strange bug in usage of abs() I encountered recently There are lots of places where we use abs , I'll replace them

问题 When compiling C/C++ codes using gcc/g++, if it ignores my register, can it tell me? For example, in this code int main() { register int j; int k; for(k = 0; k < 1000; k++) for(j = 0; j < 32000; j++) ; return 0; } j will be used as register, but in this code int main() { register int j; int k; for(k = 0; k < 1000; k++) for(j = 0; j < 32000; j++) ; int * a = &j; return 0; } j will be a normal variable. Can it tell me whether a variable I used register is really stored in a CPU register? 回答1:

问题 I have a source file which I preprocess using the options -E and -P (using GCC 4.1.2 for a vxWorks-based embedded platform). All other options are the same as when I compile the file. These options are: -Wall -march=pentium -nostdinc -O0 -fno-builtin -fno-defer-pop -g -c -o as well as all include-paths. Now when I compile this preprocessed file, the resulting object-file is much smaller (about 30%) than when I compile the original directly. And when I then link the program, the linker

问题 Hi I need to determine the mangled name of a function from within an c++ app itself. Is there any equivalent to the __FUNCDNAME__ macro in g++ ? 回答1: To get the demangled name use __PRETTY_FUNCTION__. Better is to use: #include <boost/current_function.hpp> BOOST_CURRENT_FUNCTION This gives the demangled name. I looked at cxxabi.h but there does not seem to be a mangle function. Do you really want the mangled name? 来源： https://stackoverflow.com/questions/3262585/c-get-the-mangled-names-of-a

问题 I have a makefile that creates object files for two classes (and main) and one of those classes is just defined in a .h file. In my makefile I have a line that says FileName.o: FileName.h g++ -c FileName.h but when I try to compile it says it can't find FileName.o Do I have to create FileName.cpp in order to get this to compile? 回答1: You are using your class from FileName.h somewhere, aren't you? So at least one of your .cpp files should contain #include "FileName.h" , and .h's code will be

问题 void *stackAddr[NUM_THREADS]; stackAddr[i] = malloc(STACKSIZE); The compiler (g++ 4.4.3) complains where the malloc is called... warning: pointer of type ‘void *’ used in arithmetic error: ‘void*’ is not a pointer-to-object type If you are interested in seeing the whole code, here it goes... #include <pthread.h> #include <stdio.h> #include <stdlib.h> #include <math.h> #define NUM_THREADS 4 void *stackAddr[NUM_THREADS]; pthread_t thread[NUM_THREADS]; pthread_attr_t attr; void *BusyWork(void *t

问题 I'm in the early stages (read:just started yesterday) of a project, and I'm setting up my initial makefile. It's very simplistic. Here's the full contents of the file: all: main.o resource.o g++ -o output.exe main.o resource.o main.o: main.cpp main.h resource.h g++ -mwindows -o main.o main.cpp resource.o: resource.rc windres resource.rc resource.o clean: rm *.o At this point I think it's important to mention that I'm working on Windows, so I'm doing all of this in either Powershell with MinGW

问题 I am getting undefined reference to 'mysql_suchandsuch@#' messages when trying to link my program with the MySQL libraries supplied with the 5.5 server. When MySQL was installed, I used the default path, which for me on Windows is C:\Program Files\MySQL\MySQL Server 5.5\ . Originally, I had thought that the spaces are causing my grief, but I think I've correctly worked out how to point to the library path without spaces (still with no luck). If there's another probable cause, please let me

问题 I use naked functions to patch parts of a program while it's running. I can easily do this in VC++ in Windows. I'm trying to do this in Linux and it seems gcc doesn't support naked functions. Compiling code with naked functions gives me this: warning: ‘naked’ attribute directive ignored. Compiled under CentOS 5.5 i386. 回答1: The naked attribute is only supported by GCC on certain platforms (ARM, AVR, MCORE, RX and SPU) according to the docs: naked : Use this attribute on the ARM, AVR, MCORE,