c

问题 This question already has answers here : Can I assume (bool)true == (int)1 for any C++ compiler? (4 answers) Closed 6 years ago . Consider the code bool f() { return 42; } if (f() == 1) printf("hello"); Does C (C99+ with stdbool.h) and C++ standards guarantee that "hello" will printed? Does bool a = x; is always equivalent to bool a = x ? 1 : 0; 回答1: In C++, bool is a built-in type. Conversions from any type to bool always yield false (0) or true (1). Prior to the 1999 ISO C standard, C did

问题 I have read this post. But when I tried: printf("before null %c after null\n", 0); // (ASCII=0) != '\0' ?? instead of getting: before null I got: before null after null So my question is: Is ASCII value 0 actually equal to '\0'? 回答1: Is ASCII value 0 actually equal to \0 ? Yes The differences in how the strings are stored in memory and handled by functions like printf() are important. "before null %c after null\n" "before null \0 after null\n" Both are stored in memory with an implicit \0

问题 I want to build my own scanf function. Basic idea is data from a memory address and save it to another memory address. What is stdin? Is it a memory-address like 000ffaa? If it is a memory-address what is it so I can build my own scanf function. Thanks!. 回答1: No, stdin is not "a memory address". It's an I/O stream, basically an operating-system level abstraction that allows data to be read (or written, in the case of stdout ). You need to use the proper stream-oriented I/O functions to read

问题 I'm working on a C application that interacts with a mssql database running on Windows 2008 R2. I'm able to connect to the database and run specific queries, but when i use SQLBindParameter things fall apart. I found a post on stackoverflow that appears to be the same problem, but the solution doesnt appear to be the same (Problems getting SQLBindParameter to work in C++). According to C Data types SQL_C_CHAR is correct (https://msdn.microsoft.com/en-us/library/windows/desktop/ms714556(v=vs

问题 I have read this post. But when I tried: printf("before null %c after null\n", 0); // (ASCII=0) != '\0' ?? instead of getting: before null I got: before null after null So my question is: Is ASCII value 0 actually equal to '\0'? 回答1: Is ASCII value 0 actually equal to \0 ? Yes The differences in how the strings are stored in memory and handled by functions like printf() are important. "before null %c after null\n" "before null \0 after null\n" Both are stored in memory with an implicit \0

问题 I'm working on a C application that interacts with a mssql database running on Windows 2008 R2. I'm able to connect to the database and run specific queries, but when i use SQLBindParameter things fall apart. I found a post on stackoverflow that appears to be the same problem, but the solution doesnt appear to be the same (Problems getting SQLBindParameter to work in C++). According to C Data types SQL_C_CHAR is correct (https://msdn.microsoft.com/en-us/library/windows/desktop/ms714556(v=vs

问题 I'm working on a C application that interacts with a mssql database running on Windows 2008 R2. I'm able to connect to the database and run specific queries, but when i use SQLBindParameter things fall apart. I found a post on stackoverflow that appears to be the same problem, but the solution doesnt appear to be the same (Problems getting SQLBindParameter to work in C++). According to C Data types SQL_C_CHAR is correct (https://msdn.microsoft.com/en-us/library/windows/desktop/ms714556(v=vs

问题 Consider the following snippet: char x[100]; double *p = &x; As expected, this yields this warning: f.c:3:15: warning: initialization of ‘double *’ from incompatible pointer type ‘char (*)[100]’ [-Wincompatible-pointer-types] 3 | double *p = &x; | ^ This is very easy to solve by just changing to double *p = (double*)&x; My question here is, does the casting actually DO anything? Would the code be invalid without the cast? Or is it just a way to make the compiler quiet? When is casting

问题 I have a code uses Cairo and Pango to create an image : #include<stdio.h> #include<cairo.h> #include<pango/pangocairo.h> #define IMAGE_WIDTH 650 #define IMAGE_HEIGHT 150 #define TEXT "HELLO WORLD" #define FONT "MizuFontAlphabet Normal 40" /* * $ gcc $(pkg-config pangocairo cairo --cflags --libs) file.c */ int main(int argc , char** argv) { cairo_surface_t *surface; cairo_t *cr; PangoLayout *layout; PangoFontDescription *desc; PangoRectangle extents; surface = cairo_image_surface_create(CAIRO

问题 I have a code uses Cairo and Pango to create an image : #include<stdio.h> #include<cairo.h> #include<pango/pangocairo.h> #define IMAGE_WIDTH 650 #define IMAGE_HEIGHT 150 #define TEXT "HELLO WORLD" #define FONT "MizuFontAlphabet Normal 40" /* * $ gcc $(pkg-config pangocairo cairo --cflags --libs) file.c */ int main(int argc , char** argv) { cairo_surface_t *surface; cairo_t *cr; PangoLayout *layout; PangoFontDescription *desc; PangoRectangle extents; surface = cairo_image_surface_create(CAIRO