libc

Its a small code to generate a random hermitian matrix hermitian matrix . I have called srand() before every call to rand(). but still no randomness in the output. I have used c99's complex datatype feature to create a hermitian matrix. I'm not sure where i'm wrong :( #include <stdio.h> #include <math.h> #include <complex.h> #include <stdlib.h> #include <time.h> #define MATSIZE 5 #define RAND_RANGE 100 double complex mat[MATSIZE][MATSIZE]; void gen_mat() { int i =0,j; int real; int img; for( ;i < MATSIZE; i++) { srand(time(NULL)); real = rand()%RAND_RANGE + 1; srand(time(NULL)); img = rand()

In a simple comparison test in postgres 9.1 and 8.4 is get the following weird results. postgres=# select 1 one where 'A' < 'a'; one ----- (0 rows) // ..... I would have expected 1 row postgres=# select 1 one where 'A' < 'b'; one ----- 1 (1 row) // ...... this looks OK postgres=# select 1 one where 'A' = 'a'; one ----- (0 rows) // ...... This also looks OK postgres=# select 1 one where 'A' > 'a'; one ----- 1 (1 row) // ...... This is inconsistent with the above results The ascii value of 'A' is 0x41 and 'a' is 0x61 so a straight comparison of ascii values should mean that 'A' is smaller than

When I use the function getenv() from the Standard C Library, my program inherit the environment variables from its parent. Example: $ export FOO=42 $ <<< 'int main() {printf("%s\n", getenv("FOO"));}' gcc -w -xc - && ./a.exe 42 In libc, the environ variable is declared into environ.c . I am expecting it to be empty at the execution, but I get 42 . Going a bit further getenv can be simplified as follow: char * getenv (const char *name) { size_t len = strlen (name); char **ep; uint16_t name_start; name_start = *(const uint16_t *) name; len -= 2; name += 2; for (ep = __environ; *ep != NULL; ++ep)

I am trying to build Qt 5 on a Nitrogen6x board powered by an *i.MX6Q`. I've installed Debian/wheezy on the board and am using an Ubuntu 12.10 machine for cross-compiling. Configuring Qt works like a charm but I am stuck in the make step. This is the configure script I run: ./configure -v -opensource -confirm-license -reduce-relocations -no-pch -no-xcb -no-opengl -opengl es2 -qt-libpng -qt-zlib -qt-xkbcommon -qt-xcb -qt-pcre -qt-libjpeg -qt-sql-mysql -optimized-qmake\ -make libs -device imx6 \ -compile-examples \ -device-option CROSS_COMPILE=/home/finn/gcc-linaro-arm-linux-gnueabihf-4.8-2013

On my system errno defined as: int * __error(void); #define errno (* __error()) I understand errno is a macro and expands to * __error() function: I searched everywhere (source on my system) but I can't find the definition of the __error() function, can someone show/explain what would/should be the definition of it? How the expression errno = 0 works with the above definition (Assigning 0 to a function?)? Does errno = 0 expands to * __error() = 0 ? Thanks The __error function returns a pointer to the errno variable for the calling thread. The errno macro dereferences that pointer, resulting in