SDL TTF text example

c/operator.c

@@ -288,7 +288,13 @@ int main() {
         }
     }
 
-    /* # Bitwise operators */
+    /*
+    # Bitwise operators
+
+        On signed integers: implementation defined or UB:
+        http://stackoverflow.com/questions/11644362/bitwise-operation-on-signed-integer
+        so just never do it.
+    */
     {
         /*
         # ~

gcc/README.md

@@ -6,6 +6,7 @@ Cheat on the GNU Compile Collection (GCC) language extensions and command line u
     1. [Compilation steps](compilation-steps.md)
     1. [Invocation](invocation.md)
     1. [Spec files](spec-files.md)
+    1. [GCC as library](gcc-as-library.md)
 1.  Extensions
     1.  Types
         1. [Empty struct](empty_struct.c)

gcc/asm.c

@@ -60,7 +60,7 @@
 
 #include "common.h"
 
-int main() {
+int main(void) {
 #if defined(__i386__) || defined(__x86_64__)
     puts("__i386__ || __x86_64__");
 
@@ -169,7 +169,7 @@ int main() {
         gcc will automatically put the value of `in` from RAM into a register for us
         and `out` from a register into ram at the end
 
-        note how we can do an `inc` operation directly on `%1` and `%0`
+        We can do an `inc` operation directly on both `%1` and `%0`,
         so they must both already be inside a registers as expected
 
         GCC just makes sure they are written from/to memory before/after the operations.
@@ -185,6 +185,9 @@ int main() {
             : "=r" (out)
             : "r" (in)
         );
+        /* in was not modified by inc. It had already been moved to a register. */
+        assert(in == 0);
+        /* Out was modified. But only after our custom assembly executed. */
         assert(out == 2);
     }
 
@@ -201,7 +204,7 @@ int main() {
         and minimize the use of new registers.
     */
     {
-        volatile int x = 0;
+        int x = 0;
         asm (
             "incl %0"
             : "=r" (x)
@@ -214,12 +217,14 @@ int main() {
     /*
     # Specific register constraints
 
-        `a` forces it to be put into eax.
+    # a
+
+        Forces it to be put into eax.
     */
     {
-        volatile int x = 0;
-        asm volatile (
-            "incl %0"
+        int x = 0;
+        asm (
+            "incl %%eax"
             : "=a" (x)
             : "0" (x)
         );
@@ -235,11 +240,43 @@ int main() {
     */
     {
         register int eax asm ("eax");
-        asm volatile ("mov $1, %%eax;" : : : "%eax");
+        asm ("mov $1, %%eax;" : : : "%eax");
         assert(eax == 1);
-        asm volatile ("mov $2, %%eax;" : : : "%eax");
+        asm ("mov $2, %%eax;" : : : "%eax");
         assert(eax == 2);
     }
+
+    /*
+    # modifiers
+
+        https://gcc.gnu.org/onlinedocs/gcc-4.7.0/gcc/Modifiers.html#Modifiers
+
+    # =
+
+        Says that a value may have been modified by asm.
+
+        TODO: `=` vs indicating that it is an output? (before the second `:`?
+
+    # +
+
+        Both read from and written to.
+    */
+
+    /*
+    # asm volatile
+
+        http://stackoverflow.com/questions/14449141/the-difference-between-asm-asm-volatile-and-clobbering-memory
+
+        TODO minimal example.
+    */
+
+    /*
+    # volatile variable modified in asm
+
+        TODO do you need to mark variables modified in `asm` as volatile?
+
+        I think this is exactly what the `=` modifier does already, so maybe not.
+    */
 #endif
     return EXIT_SUCCESS;
 }

gcc/gcc-as-library.md

@@ -0,0 +1,9 @@
+# GCC as library
+
+How to use GCC as a library, e.g. from another C program
+
+- <http://programmers.stackexchange.com/questions/189949/is-there-a-way-to-use-gcc-as-a-library>
+- <http://stackoverflow.com/questions/1735360/compiling-program-within-another-program-using-gcc>
+- <http://stackoverflow.com/questions/8144793/gcc-for-parsing-code>
+
+`libgccjit` from GCC 5 goes a long way.

opengl/alternatives.md

@@ -9,3 +9,28 @@ Also by Khronos.
 <http://gamedev.stackexchange.com/questions/96014/what-is-vulkan-and-how-does-it-differ-from-opengl>
 
 Derived from <https://en.wikipedia.org/wiki/Mantle_%28API%29> by AMD, now abandoned in favor of Vulkan, and will somewhat be the new OpenGL.
+
+There is no ES version like for OpenGL, <http://arstechnica.com/gadgets/2015/08/android-to-support-vulkan-graphics-api-the-open-answer-to-metal-and-dx12/> says ES and non-ES convergence has been going on for a while now.
+
+### Samples
+
+- <https://github.com/SaschaWillems/Vulkan>
+- <https://github.com/LunarG/VulkanSamples>
+
+### Hardware support
+
+Supported hardware:
+
+- NVIDIA <https://developer.nvidia.com/vulkan-driver>: Kepler and Maxwell
+- Android
+    - API 24?
+    - Samsung Galaxy S7 was the first to support it.
+
+Works on most GPUs that support OpenGL ES 3.1 <http://arstechnica.com/gadgets/2015/08/android-to-support-vulkan-graphics-api-the-open-answer-to-metal-and-dx12/>
+
+### Ubuntu install
+
+TODO. Already had an NVIDIA NVS 5400M driver 361.42 working for OpenGL.
+
+- <http://askubuntu.com/questions/774131/installing-nvidia-vulkan-drivers-for-16-04>
+- <https://github.com/SaschaWillems/Vulkan/issues/188>

posix/README.md

@@ -15,6 +15,7 @@
 1.  [getrusage](dlopen.c)
 1.  [pthread](pthread.c)
     1. [pthread_mutex](pthread_mutex.c)
+1.  [Regex](regex.c)
 1.  Networking
     1.  [socket](socket/)
     1.  [netdb.h](netdb-h.md)

posix/bibliography.md

@@ -15,3 +15,7 @@
     Very good intro do many of POSIX utilities with interesting examples and topics.
 
     The problem is that each program requires you to pass several CLI arguments to them, and just print stuff to stdout, no assertions.
+
+-   <https://github.com/hailinzeng/Unix-Network-Programming>
+
+-   <http://www.apuebook.com/index.html> Advanced Programming in the UNIX® Environment, Third Edition by Richard Stevens

posix/common.h

@@ -44,6 +44,7 @@
 
 /* POSIX only headers. */
 #include <arpa/inet.h>
+#include <curses.h>
 #include <dirent.h>
 #include <errno.h>
 #include <fcntl.h> /* creat, O_CREAT */
@@ -67,6 +68,7 @@
 #include <sys/utsname.h> /* uname, struct utsname */
 #include <sys/wait.h> /* wait, sleep */
 #include <syslog.h> /* syslog */
+#include <termios.h>
 #include <unistd.h> /* fork, ftruncate */
 
 #define TMPFILE(x) __FILE__ "__" x ".tmp"

posix/curses/Makefile

@@ -0,0 +1 @@
+../Makefile

posix/curses/Makefile_params

@@ -0,0 +1 @@
+LIBS := -lcurses

posix/curses/README.md

@@ -0,0 +1,12 @@
+# curses
+
+1.  [ncurses](ncurses.md)
+1.  Examples
+    1.  [Hello world](hello.c)
+    1.  printw
+        1. [printw newline](printw_newline.c)
+        1. [printw twice](printw_twice.c)
+        1. [printw newline screen height](printw_newline_screen_height.c)
+    1.  [clear](clear.c)
+    1.  [Check key pressed](check_key_pressed.c)
+    1.  Canonical. TODO. <http://www.gnu.org/software/libc/manual/html_node/Canonical-or-Not.html>

posix/curses/check_key_pressed.c

@@ -0,0 +1,59 @@
+/*
+Check if a key was pressed in the last loop cycle:
+http://stackoverflow.com/questions/2984307/c-key-pressed-in-linux-console
+*/
+
+#include "common.h"
+
+/*
+Return a character, on -1 if none was entered.
+*/
+int getkey(void) {
+    int character;
+    int stdin_fileno;
+    struct termios orig_term_attr;
+    struct termios new_term_attr;
+
+    stdin_fileno = fileno(stdin);
+
+    /* Save old attributes. */
+    tcgetattr(stdin_fileno, &orig_term_attr);
+
+    /* Set the terminal to raw mode. */
+    memcpy(&new_term_attr, &orig_term_attr, sizeof(struct termios));
+    /* TODO what are those parameters? */
+    new_term_attr.c_lflag &= ~(ECHO|ICANON);
+    new_term_attr.c_cc[VTIME] = 0;
+    new_term_attr.c_cc[VMIN] = 0;
+    tcsetattr(stdin_fileno, TCSANOW, &new_term_attr);
+
+    /* Read character. */
+    character = getchar();
+    while (getchar() != EOF);
+
+    /* Restore the original terminal attributes. */
+    tcsetattr(stdin_fileno, TCSANOW, &orig_term_attr);
+
+    return character;
+}
+
+int main(void) {
+    int key;
+    struct timespec sleep_cycle;
+    sleep_cycle.tv_sec = 0;
+    /*
+    If we reduce this a lot and hold da key, `-1` shows all the time.
+    When we hold a key, it it refreshed at a given low frequency it seems?
+    */
+    sleep_cycle.tv_nsec = 500000000L;
+	initscr();
+    for (;;) {
+        clear();
+        key = getkey();
+        printw("%d\n", key);
+        refresh();
+        nanosleep(&sleep_cycle, NULL);
+    }
+	endwin();
+    return 0;
+}

posix/curses/clear.c

@@ -0,0 +1,16 @@
+/* Second times overwrites the first. */
+
+#include "common.h"
+#include "common_curses.h"
+
+int main(void) {
+    int c;
+	initscr();
+	printw("before clear\n");
+	clear();
+	printw("after clear\n");
+	refresh();
+	press_any_key_to_quit();
+	endwin();
+	return 0;
+}

posix/curses/common.h

@@ -0,0 +1 @@
+../common.h

posix/curses/common_curses.h

@@ -0,0 +1,7 @@
+#define ANY_KEY_TO_QUIT_MSG "press any key to quit\n"
+
+void press_any_key_to_quit() {
+	printw(ANY_KEY_TO_QUIT_MSG);
+	refresh();
+	getch();
+}

posix/curses/hello.c

@@ -0,0 +1,13 @@
+#include <curses.h>
+
+int main(void) {
+    /* Startup. */
+	initscr();
+	printw("hello world. Press any key to quit.");
+	refresh();
+	/* Wait for use input. */
+	getch();
+	/* Teardown. */
+	endwin();
+	return 0;
+}

posix/curses/ncurses.md

@@ -0,0 +1,7 @@
+# ncurses
+
+Name of the dominant implementation.
+
+POSIX only talks about curses however.
+
+<http://stackoverflow.com/questions/1517756/whats-the-difference-between-lcurses-and-lncurses-when-compiling-c-using-ncur>

posix/curses/printw_newline.c

@@ -0,0 +1,12 @@
+/* Newlines do move the cursor down and to the beginning of the next line. */
+
+#include "common.h"
+
+int main(void) {
+	initscr();
+	printw("a\nb\npress any key to quit");
+	refresh();
+	getch();
+	endwin();
+	return 0;
+}

posix/curses/printw_newline_screen_height.c

@@ -0,0 +1,18 @@
+/*
+Bad things happen: at the bottom of the screen,
+the cursor is imply not lowered anymore.
+*/
+
+#include "common.h"
+#include "common_curses.h"
+
+int main(void) {
+    int i;
+	initscr();
+	for (i = 0; i < 1000; ++i) {
+        printw("%d\n", i);
+    }
+	press_any_key_to_quit();
+	endwin();
+	return 0;
+}

posix/curses/printw_twice.c

@@ -0,0 +1,15 @@
+/* The current cursor position is unchanged. */
+
+#include "common.h"
+#include "common_curses.h"
+
+int main(void) {
+	initscr();
+	printw("first\n");
+	printw("second\n");
+	printw(ANY_KEY_TO_QUIT_MSG);
+	refresh();
+	getch();
+	endwin();
+	return 0;
+}

posix/environ.c

@@ -8,7 +8,7 @@
 
 #include "common.h"
 
-int main() {
+int main(void) {
     /* Print entire environment. */
     extern char **environ;
     char **env = environ;

posix/interactive/sleep.c

@@ -9,7 +9,7 @@
 
 #include "common.h"
 
-int main() {
+int main(void) {
     int i = 0;
     while (1) {
         printf("%d\n", i);