Here's a patch for the website to add my changes for GCC 9 (bearing
a strong resemblance to my recent blog post)
OK to commit?
---
htdocs/gcc-9/changes.html | 310 +++++++++++++++++++++++++++++++++++++++++++++-
1 file changed, 305 insertions(+), 5 deletions(-)
diff --git a/htdocs/gcc-9/changes.html b/htdocs/gcc-9/changes.html
index e696ee1..4bdb67e 100644
--- a/htdocs/gcc-9/changes.html
+++ b/htdocs/gcc-9/changes.html
@@ -17,7 +17,7 @@ This page is a "brief" summary of some of the huge number of
improvements
in GCC 9.
<!--
You may also want to check out our
-<a href="porting_to.html">Porting to GCC 8</a> page and the
+<a href="porting_to.html">Porting to GCC 9</a> page and the
<a href="../onlinedocs/index.html#current">full GCC documentation</a>.
-->
</p>
@@ -72,6 +72,39 @@ a work-in-progress.</p>
option completion in a shell. It is intended to be used by
Bash-completion.
</li>
<li>
+ <p>
+ GCC's diagnostics now print a left-margin when printing source code
+ (via the default <a
href="https://gcc.gnu.org/onlinedocs/gcc/Diagnostic-Message-Formatting-Options.html#index-fdiagnostics-show-caret";>-fdiagnostics-show-caret</a>),
+ showing line numbers. This can be disabled via <a
href="https://gcc.gnu.org/onlinedocs/gcc/Diagnostic-Message-Formatting-Options.html#index-fno-diagnostics-show-line-numbers";>-fno-diagnostics-show-line-numbers</a>.
+ </p>
+ <p>
+ GCC's diagnostics can also now label regions of the source code to
+ show pertinent information, such as the types within an expression.
+ </p>
+<pre class="blackbg">
+$ g++ t.cc
+<span class="bold">t.cc:</span> In function '<span class="bold">int
test(const shape&, const shape&)</span>':
+<span class="bold">t.cc:15:4:</span> <span class="boldred">error: </span>no
match for '<span class="bold">operator+</span>' (operand types are
'<span class="bold">boxed_value<double></span>' and '<span
class="bold">boxed_value<double></span>')
+ 14 | return (<span class="green">width(s1) * height(s1)</span>
+ | <span class="green">~~~~~~~~~~~~~~~~~~~~~~</span>
+ | <span class="green">|</span>
+ | <span class="green">boxed_value<[...]></span>
+ 15 | <span class="boldred">+</span> <span class="blue">width(s2) *
height(s2)</span>);
+ | <span class="boldred">^</span> <span
class="blue">~~~~~~~~~~~~~~~~~~~~~~</span>
+ | <span class="blue">|</span>
+ | <span class="blue">boxed_value<[...]></span>
+</pre>
+
+ <p>
+ These labels can be disabled via <a
href="https://gcc.gnu.org/onlinedocs/gcc/Diagnostic-Message-Formatting-Options.html#index-fno-diagnostics-show-labels";>-fno-diagnostics-show-labels</a>.
+ </p>
+ </li>
+ <li>
+ A new option <a
href="https://gcc.gnu.org/onlinedocs/gcc/Diagnostic-Message-Formatting-Options.html#index-fdiagnostics-format";>-fdiagnostics-format=json</a>
+ has been introduced, for emitting diagnostics in a machine-readable
+ format.
+ </li>
+ <li>
The alignment-related options <a
href="https://gcc.gnu.org/onlinedocs/gcc/Optimize-Options.html#index-falign-functions";><code>-falign-functions</code></a>,
<a
href="https://gcc.gnu.org/onlinedocs/gcc/Optimize-Options.html#index-falign-labels";><code>-falign-labels</code></a>,
<a
href="https://gcc.gnu.org/onlinedocs/gcc/Optimize-Options.html#index-falign-loops";><code>-falign-loops</code></a>,
@@ -122,6 +155,62 @@ foo (int how)
AddressSanitizer generates more compact red-zones for automatic
variables.
That helps to reduce memory footprint of a sanitized binary.
</li>
+ <li>
+ <p>Numerous improvements have been made to the output of <a
href="https://gcc.gnu.org/onlinedocs/gcc/Developer-Options.html#index-fopt-info";>-fopt-info</a>.</p>
+ <p>
+ Messages are now prefixed with <code>optimized</code>,
+ <code>missed</code>, or <code>note</code>, rather than the old
+ behavior of all being prefixed with <code>note</code>.
+ </p>
+ <p>
+ The output from <code>-fopt-info</code> can now contain information
+ on inlining decisions:
+ </p>
+<pre class="blackbg">
+$ g++ -c inline.cc -O2 -fopt-info-inline-all
+inline.cc:24:11: note: Considering inline candidate void foreach(T, T, void
(*)(E)) [with T = char**; E = char*]/2.
+inline.cc:24:11: optimized: Inlining void foreach(T, T, void (*)(E)) [with T
= char**; E = char*]/2 into int main(int, char**)/1.
+inline.cc:19:12: missed: not inlinable: void inline_me(char*)/0 -> int
std::puts(const char*)/3, function body not available
+inline.cc:13:8: optimized: Inlined void inline_me(char*)/4 into int main(int,
char**)/1 which now has time 127.363637 and size 11, net change of +0.
+Unit growth for small function inlining: 16->16 (0%)
+
+Inlined 2 calls, eliminated 1 functions
+
+</pre>
+
+ <p>
+ The output from the vectorizer has been rationalized so that failed
+ attempts to vectorize a loop are displayed in the form
+ </p>
+ <pre>
+ [LOOP-LOCATION]: couldn't vectorize this loop
+ [PROBLEM-LOCATION]: because of [REASON]
+ </pre>
+ <p>
+ rather than an exhaustive log of all decisions made by the vectorizer.
+ For example:
+ </p>
+<pre class="blackbg">
+$ gcc -c v.c -O3 -fopt-info-all-vec
+v.c:7:3: missed: couldn't vectorize loop
+v.c:10:7: missed: statement clobbers memory: __asm__ __volatile__(""
: : : "memory");
+v.c:3:6: note: vectorized 0 loops in function.
+v.c:10:7: missed: statement clobbers memory: __asm__ __volatile__(""
: : : "memory");
+</pre>
+
+ <p>
+ The old behavior can be obtained via a new <code>-internals</code>
+ suboption of <code>-fopt-info</code>.
+ </p>
+ </li>
+ <li>
+ A new option, <a
href="https://gcc.gnu.org/onlinedocs/gcc/Developer-Options.html#index-fsave-optimization-record";>-fsave-optimization-record</a>
+ has been added, which writes a <code>SRCFILE.opt-record.json.gz</code>
+ file describing the optimization decisions made by GCC. This is
+ similar to the output of <code>-fopt-info</code>, but with additional
+ metadata such as the inlining chain, and profile information (if
+ available).
+ </li>
</ul>
<!-- .................................................................. -->
@@ -153,6 +242,17 @@ foo (int how)
member of a struct or union.
</li>
</ul></li>
+
+ <li>
+ If a macro is used with the wrong argument count, the C and C++ front
+ ends now show the definition of the macro via a <code>note</code>.
+ </li>
+
+ <li>
+ The spelling corrector now considers transposed letters, and the
+ threshold for similarity has been tightened, to avoid nonsensical
+ suggestions.
+ </li>
</ul>
<h3 id="c">C</h3>
@@ -209,6 +309,183 @@ foo (int how)
see <a href="../projects/cxx-status.html#cxx2a">the C++
status page</a>.
</li>
+
+ <li>
+ The C++ front end now preserves source locations for longer for
+ literals, <code>id-expression</code> and <code>mem-initializer</code>.
+ For example it is now able to pin-point the pertinent locations for
+ bad initializations such as these
+<pre class="blackbg">
+$ g++ -c bad-inits.cc
+<span class="bold">bad-inits.cc:10:14:</span> <span class="boldred">error:
</span>cannot convert '<span class="bold">json</span>' to '<span
class="bold">int</span>' in initialization
+ 10 | { 3, <span class="boldred">json::object</span> },
+ | <span class="boldred">~~~~~~^~~~~~</span>
+ | <span class="boldred">|</span>
+ | <span class="boldred">json</span>
+<span class="bold">bad-inits.cc:14:31:</span> <span class="boldred">error:
</span>initializer-string for array of chars is too long [<span
class="boldred">-fpermissive</span>]
+ 14 | char buffers[3][5] = { "red", <span
class="boldred">"green"</span>, "blue" };
+ | <span class="boldred">^~~~~~~</span>
+<span class="bold">bad-inits.cc:</span> In constructor '<span
class="bold">X::X()</span>':
+<span class="bold">bad-inits.cc:17:13:</span> <span class="boldred">error:
</span>invalid conversion from '<span class="bold">int</span>' to
'<span class="bold">void*</span>' [<span
class="boldred">-fpermissive</span>]
+ 17 | X() : one(<span class="boldred">42</span>), two(42), three(42)
+ | <span class="boldred">^~</span>
+ | <span class="boldred">|</span>
+ | <span class="boldred">int</span>
+</pre>
+
+ rather than emitting the error at the final closing parenthesis or
+ brace.
+ </li>
+
+ <li>
+ Error-reporting of overload resolution has been special-cased to make
+ the case of a single failed candidate easier to read. For example:
+
+<pre class="blackbg">
+$ g++ param-type-mismatch.cc
+<span class="bold">param-type-mismatch.cc:</span> In function '<span
class="bold">int test(int, const char*, float)</span>':
+<span class="bold">param-type-mismatch.cc:8:32:</span> <span
class="boldred">error: </span>cannot convert '<span class="bold">const
char*</span>' to '<span class="bold">const char**</span>'
+ 8 | return foo::member_1 (first, <span class="boldred">second</span>,
third);
+ | <span class="boldred">^~~~~~</span>
+ | <span class="boldred">|</span>
+ | <span class="boldred">const char*</span>
+<span class="bold">param-type-mismatch.cc:3:46:</span> <span
class="boldcyan">note: </span> initializing argument 2 of '<span
class="bold">static int foo::member_1(int, const char**, float)</span>'
+ 3 | static int member_1 (int one, <span class="boldcyan">const char
**two</span>, float three);
+ | <span
class="boldcyan">~~~~~~~~~~~~~^~~</span>
+</pre>
+
+
+ highlights both the problematic argument, and the parameter
+ that it can't be converted to.
+ </li>
+
+ <li>
+ Diagnostics involving binary operators now use color to distinguish the two
+ operands, and label them separately (as per the example of source
+ labelling above).
+ </li>
+
+ <li>
+ Diagnostics involving function calls now highlight the pertinent parameter
+ of the declaration in more places.
+<pre class="blackbg">
+$ g++ bad-conversion.cc
+<span class="bold">bad-conversion.cc:</span> In function '<span
class="bold">void caller()</span>':
+<span class="bold">bad-conversion.cc:9:14:</span> <span class="boldred">error:
</span>cannot convert '<span class="bold">bool</span>' to '<span
class="bold">void*</span>'
+ 9 | callee (0, <span class="boldred">false</span>, 2);
+ | <span class="boldred">^~~~~</span>
+ | <span class="boldred">|</span>
+ | <span class="boldred">bool</span>
+<span class="bold">bad-conversion.cc:3:19:</span> <span class="boldcyan">note:
</span> initializing argument 2 of '<span class="bold">void callee(int,
void*, int)</span>'
+ 3 | void callee (int, <span class="boldcyan">void *</span>, int)
+ | <span class="boldcyan">^~~~~~</span>
+</pre>
+
+ </li>
+
+ <li>
+ The C++ front end's implementation of <a
href="https://gcc.gnu.org/onlinedocs/gcc/Warning-Options.html#index-Wformat";>-Wformat</a>
+ now shows precise locations within string literals, and underlines
+ the pertinent arguments at bogus call sites (the C front end has done
+ this since GCC 7). For example:
+<pre class="blackbg">
+$ g++ -c bad-printf.cc -Wall
+<span class="bold">bad-printf.cc:</span> In function '<span
class="bold">void print_field(const char*, float, long int, long
int)</span>':
+<span class="bold">bad-printf.cc:6:17:</span> <span
class="boldmagenta">warning: </span>field width specifier '<span
class="bold">*</span>' expects argument of type '<span
class="bold">int</span>', but argument 3 has type '<span
class="bold">long int</span>' [<span class="boldmagenta">-Wformat=</span>]
+ 6 | printf ("%s: <span class="boldmagenta">%*ld</span> ",
fieldname, <span class="green">column - width</span>, value);
+ | <span class="boldmagenta">~^~~</span>
<span class="green">~~~~~~~~~~~~~~</span>
+ | <span class="boldmagenta">|</span>
<span class="green">|</span>
+ | <span class="boldmagenta">int</span>
<span class="green">long int</span>
+<span class="bold">bad-printf.cc:6:19:</span> <span
class="boldmagenta">warning: </span>format '<span
class="bold">%ld</span>' expects argument of type '<span
class="bold">long int</span>', but argument 4 has type '<span
class="bold">double</span>' [<span class="boldmagenta">-Wformat=</span>]
+ 6 | printf ("%s: <span class="boldmagenta">%*ld</span> ",
fieldname, column - width, <span class="green">value</span>);
+ | <span class="boldmagenta">~~~^</span>
<span class="green">~~~~~</span>
+ | <span class="boldmagenta">|</span>
<span class="green">|</span>
+ | <span class="boldmagenta">long int</span>
<span class="green">double</span>
+ | <span class="green">%*f</span>
+</pre>
+
+ </li>
+
+ <li>
+ The C++ front end has gained new fix-it hints for forgetting the
+ <code>return *this;</code> needed by various C++ operators:
+
+<pre class="blackbg">
+$ g++ -c operator.cc
+<span class="bold">operator.cc:</span> In member function '<span
class="bold">boxed_ptr& boxed_ptr::operator=(const
boxed_ptr&)</span>':
+<span class="bold">operator.cc:7:3:</span> <span class="boldmagenta">warning:
</span>no return statement in function returning non-void [<span
class="boldmagenta">-Wreturn-type</span>]
+ 6 | m_ptr = other.m_ptr;
+ +++ |+<span class="green"> return *this;</span>
+ 7 | <span class="boldmagenta">}</span>
+ | <span class="boldmagenta">^</span>
+</pre>
+
+
+ for when the compiler needs a <code>typename</code>:
+
+<pre class="blackbg">
+$ g++ -c template.cc
+<span class="bold">template.cc:3:3:</span> <span class="boldred">error:
</span>need '<span class="bold">typename</span>' before '<span
class="bold">Traits::type</span>' because '<span
class="bold">Traits</span>' is a dependent scope
+ 3 | <span class="boldred">Traits</span>::type type;
+ | <span class="boldred">^~~~~~</span>
+ | <span class="green">typename </span>
+</pre>
+
+
+ when trying to use an accessor member as if it were a data member:
+
+<pre class="blackbg">
+$ g++ -c fncall.cc
+<span class="bold">fncall.cc:</span> In function '<span class="bold">void
hangman(const mystring&)</span>':
+<span class="bold">fncall.cc:12:11:</span> <span class="boldred">error:
</span>invalid use of member function '<span class="bold">int
mystring::get_length() const</span>' (did you forget the '<span
class="bold">()</span>' ?)
+ 12 | if (<span class="boldred">str.get_length</span> > 0)
+ | <span class="boldred">~~~~^~~~~~~~~~</span>
+ | <span class="green">()</span>
+</pre>
+
+
+ for C++11's scoped enums:
+
+<pre class="blackbg">
+$ g++ -c enums.cc
+<span class="bold">enums.cc:</span> In function '<span class="bold">void
json::test(const json::value&)</span>':
+<span class="bold">enums.cc:12:26:</span> <span class="boldred">error:
</span>'<span class="bold">STRING</span>' was not declared in this
scope; did you mean '<span class="bold">json::kind::STRING</span>'?
+ 12 | if (v.get_kind () == <span class="boldred">STRING</span>)
+ | <span class="boldred">^~~~~~</span>
+ | <span class="green">json::kind::STRING</span>
+<span class="bold">enums.cc:3:44:</span> <span class="boldcyan">note:
</span>'<span class="bold">json::kind::STRING</span>' declared here
+ 3 | enum class kind { OBJECT, ARRAY, NUMBER, <span
class="boldcyan">STRING</span>, TRUE, FALSE, NULL_ };
+ | <span
class="boldcyan">^~~~~~</span>
+</pre>
+
+
+ and a tweak to integrate the suggestions about misspelled members
+ with that for accessors:
+
+<pre class="blackbg">
+$ g++ -c accessor-fixit.cc
+<span class="bold">accessor-fixit.cc:</span> In function '<span
class="bold">int test(t*)</span>':
+<span class="bold">accessor-fixit.cc:17:15:</span> <span
class="boldred">error: </span>'<span class="bold">class t</span>' has
no member named '<span class="bold">ratio</span>'; did you mean
'<span class="bold">int t::m_ratio</span>'? (accessible via
'<span class="bold">int t::get_ratio() const</span>')
+ 17 | return ptr-><span class="boldred">ratio</span>;
+ | <span class="boldred">^~~~~</span>
+ | <span class="green">get_ratio()</span>
+</pre>
+
+
+ In addition, various diagnostics in the C++ front-end have been
+ streamlined by consolidating the suggestion into the initial
+ error, rather than emitting a follow-up note:
+
+<pre class="blackbg">
+$ g++ typo.cc
+<span class="bold">typo.cc:5:13:</span> <span class="boldred">error:
</span>'<span class="bold">BUFSIZE</span>' was not declared in this
scope; did you mean '<span class="bold">BUF_SIZE</span>'?
+ 5 | uint8_t buf[<span class="boldred">BUFSIZE</span>];
+ | <span class="boldred">^~~~~~~</span>
+ | <span class="green">BUF_SIZE</span>
+</pre>
+
+
+ </li>
</ul>
<h4 id="libstdcxx">Runtime Library (libstdc++)</h4>
@@ -311,7 +588,13 @@ foo (int how)
<!-- <h3 id="go">Go</h3> -->
<!-- .................................................................. -->
-<!-- <h2 id="jit">libgccjit</h2> -->
+<h2 id="jit">libgccjit</h2>
+
+<ul>
+ <li>
+ The libgccjit API gained a new entry point: <a
href="https://gcc.gnu.org/onlinedocs/jit/topics/contexts.html#gcc_jit_context_add_driver_option";>gcc_jit_context_add_driver_option</a>.
+ </li>
+</ul>
<!-- .................................................................. -->
<h2 id="targets">New Targets and Target Specific Improvements</h2>
@@ -494,11 +777,28 @@ foo (int how)
<!-- .................................................................. -->
-<!-- <h2 id="plugins">Improvements for plugin authors</h2> -->
+<h2 id="plugins">Improvements for plugin authors</h2>
+<ul>
+ <li>
+ GCC's diagnostic subsystem now has a way to logically group together
+ related diagnostics, <code>auto_diagnostic_group</code>. Such
+ diagnostics will be nested by the output of <a
href="https://gcc.gnu.org/onlinedocs/gcc/Diagnostic-Message-Formatting-Options.html#index-fdiagnostics-format";>-fdiagnostics-format=json</a>.
+ </li>
-<!-- .................................................................. -->
-<!-- <h2>Other significant improvements</h2> -->
+ <li>
+ GCC now has a set of <a
href="https://gcc.gnu.org/onlinedocs/gccint/User-Experience-Guidelines.html";>user
experience guidelines for GCC</a>,
+ with information and advice on implementing new diagnostics.
+ </li>
+</ul>
+<!-- .................................................................. -->
+<h2>Other significant improvements</h2>
+<ul>
+ <li>
+ GCC's internal "selftest" suite now runs for C++ as well as C (in
+ debug builds of the compiler).
+ </li>
+</ul>
<!-- .................................................................. -->
<!-- <h2 id="9.1">GCC 9.1</h2> -->
--
1.8.5.3
