Hello.
I would like to document features I prepared in time frame of GCC 8.
Martin
Index: htdocs/gcc-8/changes.html
===================================================================
RCS file: /cvs/gcc/wwwdocs/htdocs/gcc-8/changes.html,v
retrieving revision 1.51
diff --unified -r1.51 changes.html
--- htdocs/gcc-8/changes.html 3 Apr 2018 06:52:04 -0000 1.51
+++ htdocs/gcc-8/changes.html 3 Apr 2018 11:13:31 -0000
@@ -113,6 +113,93 @@
possible for the user to have a finer-grained control over the loop
unrolling optimization.
</li>
+ <li>
+ GCOV tool can distinguish functions that begin on a same line in
+ a source file. This can be a different template instantiation or
+ a class constructor:
+ <blockquote><pre>
+File 'ins.C'
+Lines executed:100.00% of 8
+Creating 'ins.C.gcov'
+
+ -: 0:Source:ins.C
+ -: 0:Graph:ins.gcno
+ -: 0:Data:ins.gcda
+ -: 0:Runs:1
+ -: 0:Programs:1
+ -: 1:template<class T>
+ -: 2:class Foo
+ -: 3:{
+ -: 4: public:
+ 2: 5: Foo(): b (1000) {}
+------------------
+Foo<char>::Foo():
+ 1: 5: Foo(): b (1000) {}
+------------------
+Foo<int>::Foo():
+ 1: 5: Foo(): b (1000) {}
+------------------
+ 2: 6: void inc () { b++; }
+------------------
+Foo<char>::inc():
+ 1: 6: void inc () { b++; }
+------------------
+Foo<int>::inc():
+ 1: 6: void inc () { b++; }
+------------------
+ -: 7:
+ -: 8: private:
+ -: 9: int b;
+ -: 10:};
+ -: 11:
+ 1: 12:int main(int argc, char **argv)
+ -: 13:{
+ 1: 14: Foo<int> a;
+ 1: 15: Foo<char> b;
+ -: 16:
+ 1: 17: a.inc ();
+ 1: 18: b.inc ();
+ 1: 19:}
+ </pre></blockquote>
+ </li>
+ <li>GCOV has more accurate numbers for execution of source line executions.</li>
+ <li>GCOV tool can use TERM colors to provide more readable output.</li>
+ <li>AddressSanitizer gained a new pair of sanitization options,
+ -fsanitize=pointer-compare and -fsanitize=pointer-subtract, which
+ warn about subtraction (or comparison) of pointers that point to
+ a different memory object:
+ <blockquote><pre>
+int
+main ()
+{
+ /* Heap allocated memory. */
+ char *heap1 = (char *)__builtin_malloc (42);
+ char *heap2 = (char *)__builtin_malloc (42);
+ if (heap1 > heap2)
+ return 1;
+
+ return 0;
+}
+
+<span class="boldred">==17465==ERROR: AddressSanitizer: invalid-pointer-pair: 0x604000000010 0x604000000050</span>
+ #0 0x40070f in main /tmp/pointer-compare.c:7
+ #1 0x7ffff6a72a86 in __libc_start_main (/lib64/libc.so.6+0x21a86)
+ #2 0x400629 in _start (/tmp/a.out+0x400629)
+
+<span class="boldlime">0x604000000010 is located 0 bytes inside of 42-byte region [0x604000000010,0x60400000003a)</span>
+allocated by thread T0 here:
+ #0 0x7ffff6efb390 in __interceptor_malloc ../../../../libsanitizer/asan/asan_malloc_linux.cc:86
+ #1 0x4006ea in main /tmp/pointer-compare.c:5
+ #2 0x7ffff6a72a86 in __libc_start_main (/lib64/libc.so.6+0x21a86)
+
+<span class="boldlime">0x604000000050 is located 0 bytes inside of 42-byte region [0x604000000050,0x60400000007a)</span>
+allocated by thread T0 here:
+ #0 0x7ffff6efb390 in __interceptor_malloc ../../../../libsanitizer/asan/asan_malloc_linux.cc:86
+ #1 0x4006f8 in main /tmp/pointer-compare.c:6
+ #2 0x7ffff6a72a86 in __libc_start_main (/lib64/libc.so.6+0x21a86)
+
+SUMMARY: AddressSanitizer: invalid-pointer-pair /tmp/pointer-compare.c:7 in main
+ </li>
</ul>
@@ -187,7 +274,9 @@
<h3 id="cxx">C++</h3>
<ul>
- <li></li>
+ <li>Having a non-void function that does not return a value is considered as
+ undefined behavior. The compiler considers such code as unreachable and
+ makes more aggressive optimizations based on that.</li>
</ul>
<h3 id="fortran">Fortran</h3>
