@@ -8,16 +8,15 @@
 # by the Makefile default values.
 MYCC            ?= gcc
 MYCXX           ?= g++
-D               ?= #-D_XOPEN_SOURCE 700
 G               ?= gdb3
 I               ?= #-I/usr/include
 O               ?= 0
 STD             ?= c11
 PEDANTIC        ?= -pedantic-errors
-CFLAGS          ?= $(D) -g$(G) -O$(O) -std=$(STD) -Wextra $(PEDANTIC) $(CFLAGS_EXTRA)
-MYCXXFLAGS      ?= $(D) -g$(G) -O$(O) -std=c++11  -Wextra $(PEDANTIC) $(CXXFLAGS_EXTRA)
+CFLAGS          ?= -g$(G) -O$(O) -pthread -std=$(STD) -Wextra $(PEDANTIC) $(CFLAGS_EXTRA)   #-pg 
+MYCXXFLAGS      ?= -g$(G) -O$(O) -pthread -std=c++11  -Wextra $(PEDANTIC) $(CXXFLAGS_EXTRA) #-pg 
 
-LIBS            ?= -lm -pthread #-lGL -lGLU -lglut
+LIBS            ?= -lm #-lGL -lGLU -lglut
 
 # Fortran
 FF      ?= gfortran
 
@@ -25,6 +25,7 @@ Relies on [C++ boilerplate](https://github.com/cirosantilli/cpp-boilerplate) to
     1.  [C from C++](c-from-cpp/)
     1.  [C++ from C](cpp-from-c/)
     1.  [Fortran from C](fortran-from-c/)
+1.  [gprof](gprof.md)
 1.  [GDB](gdb/)
 1.  [Boost](boost/)
 1.  [CMake](cmake.md)
 
@@ -20,6 +20,10 @@
 
     Many behaviour examples.
 
+-   Design and Evolution of C++ <http://www.stroustrup.com/dne.html>
+
+    Ultimate source for "Why is the language designed like that" questions.
+
 -   <http://www.parashift.com/c++-faq/index.html>
 
     C++ FAQ.
@@ -52,6 +56,10 @@
 
     Hardcore optimization tutorials for C++ and assembly.
 
+-   <http://www.open-std.org/jtc1/sc22/wg21/docs/cwg_active.html>
+
+    C++ specification official bug tracker.
+
 ## Non-free
 
 -   <http://stackoverflow.com/questions/388242/the-definitive-c-book-guide-and-list>
 
@@ -1,15 +1,17 @@
 CFLAGS_EXTRA := \
+  -DIMPLEMENTATION_SIGNAL \
+  -DUNDEFINED_BEHAVIOUR \
+  -trigraphs \
   -Wno-comment \
   -Wno-ignored-qualifiers \
   -Wno-missing-field-initializers \
   -Wno-overflow \
   -Wno-override-init \
   -Wno-sequence-point \
   -Wno-sign-compare \
-  -Wno-uninitialized
+  -Wno-uninitialized \
   -Wno-unused-but-set-variable \
   -Wno-unused-label \
   -Wno-unused-local-typedefs \
   -Wno-unused-value \
-  -Wno-unused-variable \
-DEFINES := -DIMPLEMENTATION_SIGNAL -DUNDEFINED_BEHAVIOUR
+  -Wno-unused-variable
@@ -37,14 +37,24 @@
             1.  [_Generic](generic.c)
             1.  [Constant expression](constant_expression.c)
                 1. [_Static_assert](static_assert.c)
+        1.  [Pointer](pointer.c)
+    1.  Branching
+        1. [if](if.c)
+        1. [while](while.c)
+        1. [switch](switch.c)
+        1. [goto](goto.c)
     1.  [Function](function.c)
         1. [Function pointer](function_pointer.c)
         1. [inline](inline.c)
         1. [Static array argument](static_array_argument.c)
         1. [_Noreturn](noreturn.c)
-    1.  [Preprocessor](preprocessor.c)
-        1. [cpp](cpp.sh)
+    1.  [Operator](operator.c)
+    1.  [Sequence point](sequence_point.c)
+    1.  Preprocessor
+        [Preprocessor inside C](preprocessor.c)
+        [Preprocessor in isolation](preprocessor.sh)
     1.  [Signal](signal.c)
+    1.  [Trigraph](trigraph.c)
     1.  Multi-file
         1.  [static](static.c)
         1.  [extern](extern.c)
@@ -53,13 +63,17 @@
         1. [NDEBUG](ndebug.c)
         1. [assert fail](interactive/assert_fail.c)
     1.  [stdio.h](stdio_h.c)
+        [printf](printf.c)
     1.  [stdint.h](stdint_h.c)
-    1.  stdlib.h
+    1.  [stdlib.h](stdlib_h.c)
+        1.  Exit related
+            1. [exit()](exit.c)
+            1. [atexit()](atexit.c)
+            1. [abort()](interactive/abort.c.off)
+            1. [abort()](interactive/abort.c.off)
+        1. [abs()](abs.c)
         1. [malloc()](malloc.c)
-        1. [exit()](exit.c)
-        1. [atexit()](atexit.c)
-        1. [abort()](interactive/abort.c.off)
-    1.  stddef.h
+        1. [getenv](getenv.c)
         1. [offsetof()](offsetof.c)
     1.  [string.h](string_h.c)
     1.  [ctype.h](ctype_h.c)
@@ -73,6 +87,7 @@
     1.  [varargs_h](varargs_h.c)
     1.  [errno.h](errno_h.c)
     1.  [iso646.h](iso646_h.c)
+    1.  [setjmp.h](setjmp_h.c)
 1.  Applications
     1. [User input](interactive/user_input.c.off)
     1. [Design patterns](design_patterns.c)
 
@@ -0,0 +1,28 @@
+/*
+# abs
+
+    Absolute values, integer version.
+
+    For floating point values, use `fabs` in `math.h`.
+*/
+
+#include "common.h"
+
+int main() {
+    assert(abs(-1) == 1);
+
+    /*
+    There is one UB case in 2's complement: INT_MIN
+
+    TODO can there be more or less UB cases?
+    */
+    {
+#ifdef UNDEFINED_BEHAVIOUR
+        printf("abs(INT_MIN) = 0x%x\n", abs(INT_MIN));
+        /* For comparison only. */
+        printf("INT_MIN      = 0x%x\n", INT_MIN);
+#endif
+    }
+
+    return EXIT_SUCCESS;
+}
@@ -3,7 +3,7 @@
 #include <errno.h>
 #include <fenv.h>
 #include <float.h>
-#include <inttypes.h> /* PRIxPTR */
+#include <inttypes.h> /* PRIxPTR,  */
 #include <iso646.h>
 #include <limits.h> /* *_MAX, *_MIN for integer types */
 #include <locale.h>
 
@@ -14,6 +14,8 @@
 
     -   only constant expressions can be used in `_Static_assert`
 
+    -   only constant expressions can be used in `case` expressions
+
     C++ does not allow const pointer typecasts, so `const` variables generate constant expressions.
     There is an even more explicit language feature in C++11 via the `constexpr` keyword.
 */
 
@@ -62,6 +62,19 @@ int main() {
                     assert(e == -1);
                 }
             }
+
+            /*
+            Repeat values.
+
+            Seems legal: http://stackoverflow.com/questions/5561142/duplicate-enum-values-in-c
+            */
+            {
+                enum E {
+                    E0 = 0,
+                    E0_2 = 0
+                };
+                assert(E0 == E0_2);
+            }
         }
 
         /*
@@ -176,7 +189,7 @@ int main() {
 
         /* ERROR: lvalue required */
         /* Enum constans are not lvalues. */
-        /*int *pe = &E1;*/
+        /*int *pe = &E0;*/
 
         /* TODO legal but useless? */
         enum E *pe;