@@ -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.
+    */
     {
         /*
         # ~
 
@@ -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)
 
@@ -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;
 }
@@ -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.
@@ -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>
@@ -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)
 
@@ -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
@@ -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"
 
@@ -0,0 +1 @@
+../Makefile
@@ -0,0 +1 @@
+LIBS := -lcurses
Original file line number	Diff line number	Diff line change
`@@ -288,7 +288,13 @@ int main() {`
`288`	`288`	`}`
`289`	`289`	`}`
`290`	`290`
`291`		`- /* # Bitwise operators */`
	`291`	`+ /*`
	`292`	`+ # Bitwise operators`
	`293`	`+`
	`294`	`+ On signed integers: implementation defined or UB:`
	`295`	`+ http://stackoverflow.com/questions/11644362/bitwise-operation-on-signed-integer`
	`296`	`+ so just never do it.`
	`297`	`+ */`
`292`	`298`	`{`
`293`	`299`	`/*`
`294`	`300`	`# ~`