r199970 - Update page on clang diagnostics to contrast to GCC 4.9 instead of 4.2. A lot
Richard Smith
metafoo at gmail.com
Thu Jan 23 20:11:25 PST 2014
On Thu Jan 23 2014 at 8:08:46 PM, Nico Weber <thakis at chromium.org> wrote:
> They have at least a flag to turn it on:
> http://llvm.org/viewvc/llvm-project?view=revision&revision=179728
>
> Maybe it's not on by default though?
>
They have a flag, but it appears to be off by default. (At least, I built
and ran GCC trunk, and it produced caret diagnostics but no colors for me.)
> On Thu, Jan 23, 2014 at 8:04 PM, Sean Silva <silvas at purdue.edu> wrote:
>
> Does GCC's output still not have color?
>
> -- Sean Silva
>
>
> On Thu, Jan 23, 2014 at 10:13 PM, Richard Smith <
> richard-llvm at metafoo.co.uk> wrote:
>
> Author: rsmith
> Date: Thu Jan 23 21:13:34 2014
> New Revision: 199970
>
> URL: http://llvm.org/viewvc/llvm-project?rev=199970&view=rev
> Log:
> Update page on clang diagnostics to contrast to GCC 4.9 instead of 4.2. A
> lot
> of the differences we identified here have been fixed by improvements in
> GCC.
>
> Modified:
> cfe/trunk/www/diagnostics.html
>
> Modified: cfe/trunk/www/diagnostics.html
> URL:
> http://llvm.org/viewvc/llvm-project/cfe/trunk/www/diagnostics.html?rev=199970&r1=199969&r2=199970&view=diff
>
> ==============================================================================
> --- cfe/trunk/www/diagnostics.html (original)
> +++ cfe/trunk/www/diagnostics.html Thu Jan 23 21:13:34 2014
> @@ -7,10 +7,14 @@
> <link type="text/css" rel="stylesheet" href="menu.css">
> <link type="text/css" rel="stylesheet" href="content.css">
> <style type="text/css">
> - .warn { color:magenta; }
> - .err { color:red; }
> - .snip { color:darkgreen; }
> - .point { color:blue; }
> + .loc { font-weight: bold; }
> + .err { color:red; font-weight: bold; }
> + .warn { color:magenta; font-weight: bold; }
> + .note { color:gray; font-weight: bold; }
> + .msg { font-weight: bold; }
> + .cmd { font-style: italic; }
> + .snip { }
> + .point { color:green; font-weight: bold; }
> </style>
> </head>
> <body>
> @@ -29,10 +33,7 @@ friendly. As far as a command-line comp
> making the diagnostics (error and warning messages) generated by the
> compiler
> be as useful as possible. There are several ways that we do this. This
> section
> talks about the experience provided by the command line compiler,
> contrasting
> -Clang output to GCC 4.2's output in several examples.
> -<!--
> -Other clients
> -that embed Clang and extract equivalent information through internal
> APIs.-->
> +Clang output to GCC 4.9's output in some cases.
> </p>
>
> <h2>Column Numbers and Caret Diagnostics</h2>
> @@ -41,25 +42,35 @@ that embed Clang and extract equivalent
> information. The clang command-line compiler driver uses this information
> to print "point diagnostics".
> (IDEs can use the information to display in-line error markup.)
> -Precise error location in the source is a feature provided by many
> commercial
> -compilers, but is generally missing from open source
> -compilers. This is nice because it makes it very easy to understand
> exactly
> -what is wrong in a particular piece of code</p>
> +This is nice because it makes it very easy to understand exactly
> +what is wrong in a particular piece of code.</p>
>
> -<p>The point (the blue "^" character) exactly shows where the problem is,
> even
> +<p>The point (the green "^" character) exactly shows where the problem
> is, even
> inside of a string. This makes it really easy to jump to the problem and
> -helps when multiple instances of the same character occur on a line.
> (We'll
> +helps when multiple instances of the same character occur on a line.
> (We'll
> revisit this more in following examples.)</p>
>
> <pre>
> - $ <b>gcc-4.2 -fsyntax-only -Wformat format-strings.c</b>
> - format-strings.c:91: warning: too few arguments for format
> - $ <b>clang -fsyntax-only format-strings.c</b>
> - format-strings.c:91:13: <span class="warn">warning:</span> '.*'
> specified field precision is missing a matching 'int' argument
> - <span class="snip"> printf("%.*d");</span>
> + $ <span class="cmd">gcc-4.9 -fsyntax-only -Wformat
> format-strings.c</span>
> + format-strings.c: In function 'void f()':
> + format-strings.c:91:16: warning: field precision specifier '.*' expects
> a matching 'int' argument [-Wformat=]
> + printf("%.*d");
> + ^
> + format-strings.c:91:16: warning: format '%d' expects a matching 'int'
> argument [-Wformat=]
> + $ <span class="cmd">clang -fsyntax-only format-strings.c</span>
> + <span class="loc">format-strings.c:91:13:</span> <span
> class="warn">warning:</span> <span class="msg">'.*' specified field
> precision is missing a matching 'int' argument</span>
> + <span class="snip" > printf("%.*d");</span>
> <span class="point"> ^</span>
> </pre>
>
> +<p>Note that modern versions of GCC have followed Clang's lead, and are
> +now able to give a column for a diagnostic, and include a snippet of
> source
> +text in the result. However, Clang's column number is much more accurate,
> +pointing at the problematic format specifier, rather than the <tt>)</tt>
> +character the parser had reached when the problem was detected.
> +Also, Clang's diagnostic is colored by default, making it easier to
> +distinguish from nearby text.</p>
> +
> <h2>Range Highlighting for Related Text</h2>
>
> <p>Clang captures and accurately tracks range information for expressions,
> @@ -74,11 +85,14 @@ Range information is very useful for
> cases involving precedence issues and many other cases.</p>
>
> <pre>
> - $ <b>gcc-4.2 -fsyntax-only t.c</b>
> - t.c:7: error: invalid operands to binary + (have 'int' and 'struct A')
> - $ <b>clang -fsyntax-only t.c</b>
> - t.c:7:39: <span class="err">error:</span> invalid operands to binary
> expression ('int' and 'struct A')
> - <span class="snip"> return y + func(y ? ((SomeA.X + 40) + SomeA) / 42
> + SomeA.X : SomeA.X);</span>
> + $ <span class="cmd">gcc-4.9 -fsyntax-only t.c</span>
> + t.c: In function 'int f(int, int)':
> + t.c:7:39: error: invalid operands to binary + (have 'int' and 'struct
> A')
> + return y + func(y ? ((SomeA.X + 40) + SomeA) / 42 + SomeA.X :
> SomeA.X);
> + ^
> + $ <span class="cmd">clang -fsyntax-only t.c</span>
> + <span class="loc">t.c:7:39:</span> <span class="err">error:</span>
> <span class="msg">invalid operands to binary expression ('int' and 'struct
> A')</span>
> + <span class="snip" > return y + func(y ? ((SomeA.X + 40) + SomeA) / 42
> + SomeA.X : SomeA.X);</span>
> <span class="point"> ~~~~~~~~~~~~~~ ^ ~~~~~</span>
> </pre>
>
> @@ -90,62 +104,24 @@ why. In the example above, we tell you
> the left and right hand sides, and we don't repeat what is obvious from
> the
> point (e.g., that this is a "binary +").</p>
>
> -<p>Many other examples abound. In the following example, not only do we
> tell you that there is a problem with the *
> +<p>Many other examples abound. In the following example, not only do we
> tell you
> +that there is a problem with the <tt>*</tt>
> and point to it, we say exactly why and tell you what the type is (in
> case it is
> a complicated subexpression, such as a call to an overloaded function).
> This
> sort of attention to detail makes it much easier to understand and fix
> problems
> quickly.</p>
>
> <pre>
> - $ <b>gcc-4.2 -fsyntax-only t.c</b>
> - t.c:5: error: invalid type argument of 'unary *'
> - $ <b>clang -fsyntax-only t.c</b>
> - t.c:5:11: <span class="err">error:</span> indirection requires pointer
> operand ('int' invalid)
> - <span class="snip"> int y = *SomeA.X;</span>
> + $ <span class="cmd">gcc-4.9 -fsyntax-only t.c</span>
> + t.c:5:11: error: invalid type argument of unary '*' (have 'int')
> + return *SomeA.X;
> + ^
> + $ <span class="cmd">clang -fsyntax-only t.c</span>
> + <span class="loc">t.c:5:11:</span> <span class="err">error:</span>
> <span class="msg">indirection requires pointer operand ('int'
> invalid)</span>
> + <span class="snip" > int y = *SomeA.X;</span>
> <span class="point"> ^~~~~~~~</span>
> </pre>
>
> -<h2>No Pretty Printing of Expressions in Diagnostics</h2>
> -
> -<p>Since Clang has range highlighting, it never needs to pretty print
> your code
> -back out to you. GCC can produce inscrutible error messages in some
> cases when
> -it tries to do this. In this example P and Q have type "int*":</p>
> -
> -<pre>
> - $ <b>gcc-4.2 -fsyntax-only t.c</b>
> - #'exact_div_expr' not supported by pp_c_expression#'t.c:12: error:
> called object is not a function
> - $ <b>clang -fsyntax-only t.c</b>
> - t.c:12:8: <span class="err">error:</span> called object type 'int' is
> not a function or function pointer
> - <span class="snip"> (P-Q)();</span>
> - <span class="point"> ~~~~~^</span>
> -</pre>
> -
> -<p>This can be particularly bad in G++, which often emits errors
> - containing lowered vtable references. For example:</p>
> -
> -<pre>
> - $ <b>cat t.cc</b>
> - struct a {
> - virtual int bar();
> - };
> -
> - struct foo : public virtual a {
> - };
> -
> - void test(foo *P) {
> - return P->bar() + *P;
> - }
> - $ <b>gcc-4.2 t.cc</b>
> - t.cc: In function 'void test(foo*)':
> - t.cc:9: error: no match for 'operator+' in '(((a*)P) + (*(long
> int*)(P->foo::<anonymous>.a::_vptr$a +
> -0x00000000000000020)))->a::bar() + * P'
> - t.cc:9: error: return-statement with a value, in function returning
> 'void'
> - $ <b>clang t.cc</b>
> - t.cc:9:18: <span class="err">error:</span> invalid operands to binary
> expression ('int' and 'foo')
> - <span class="snip"> return P->bar() + *P;</span>
> - <span class="point"> ~~~~~~~~ ^ ~~</span>
> -</pre>
> -
> -
> <h2>Typedef Preservation and Selective Unwrapping</h2>
>
> <p>Many programmers use high-level user defined types, typedefs, and other
> @@ -156,15 +132,11 @@ trivial types and it is important to str
> is going on. Clang aims to handle both cases well.<p>
>
> <p>The following example shows where it is important to preserve
> -a typedef in C. Here the type printed by GCC isn't even valid, but if the
> error
> -were about a very long and complicated type (as often happens in C++) the
> error
> -message would be ugly just because it was long and hard to read.</p>
> +a typedef in C.</p>
>
> <pre>
> - $ <b>gcc-4.2 -fsyntax-only t.c</b>
> - t.c:15: error: invalid operands to binary / (have 'float __vector__'
> and 'const int *')
> - $ <b>clang -fsyntax-only t.c</b>
> - t.c:15:11: <span class="err">error:</span> can't convert between vector
> values of different size ('__m128' and 'int const *')
> + $ <span class="cmd">clang -fsyntax-only t.c</span>
> + <span class="loc">t.c:15:11:</span> <span class="err">error:</span>
> <span class="msg">can't convert between vector values of different size
> ('__m128' and 'int const *')</span>
> <span class="snip"> myvec[1]/P;</span>
> <span class="point"> ~~~~~~~~^~</span>
> </pre>
> @@ -174,10 +146,8 @@ underlying details of a typedef. If the
> system "pid_t" typedef is defined, Clang helpfully displays it with
> "aka".</p>
>
> <pre>
> - $ <b>gcc-4.2 -fsyntax-only t.c</b>
> - t.c:13: error: request for member 'x' in something not a structure or
> union
> - $ <b>clang -fsyntax-only t.c</b>
> - t.c:13:9: <span class="err">error:</span> member reference base type
> 'pid_t' (aka 'int') is not a structure or union
> + $ <span class="cmd">clang -fsyntax-only t.c</span>
> + <span class="loc">t.c:13:9:</span> <span class="err">error:</span>
> <span class="msg">member reference base type 'pid_t' (aka 'int') is not a
> structure or union</span>
> <span class="snip"> myvar = myvar.x;</span>
> <span class="point"> ~~~~~ ^</span>
> </pre>
> @@ -202,13 +172,11 @@ void addHTTPService(servers::Server cons
> </pre>
> </blockquote>
>
> -<p>and then compile it, we see that Clang is both providing more accurate
> information and is retaining the types as written by the user (e.g.,
> "servers::Server", "::services::WebService"):
> +<p>and then compile it, we see that Clang is both providing accurate
> information and is retaining the types as written by the user (e.g.,
> "servers::Server", "::services::WebService"):
>
> <pre>
> - $ <b>g++-4.2 -fsyntax-only t.cpp</b>
> - t.cpp:9: error: no match for 'operator+=' in 'server += http'
> - $ <b>clang -fsyntax-only t.cpp</b>
> - t.cpp:9:10: <span class="err">error:</span> invalid operands to binary
> expression ('servers::Server const' and '::services::WebService const *')
> + $ <span class="cmd">clang -fsyntax-only t.cpp</span>
> + <span class="loc">t.cpp:9:10:</span> <span class="err">error:</span>
> <span class="msg">invalid operands to binary expression ('servers::Server
> const' and '::services::WebService const *')</span>
> <span class="snip">server += http;</span>
> <span class="point">~~~~~~ ^ ~~~~</span>
> </pre>
> @@ -216,10 +184,8 @@ void addHTTPService(servers::Server cons
> <p>Naturally, type preservation extends to uses of templates, and Clang
> retains information about how a particular template specialization (like
> <code>std::vector<Real></code>) was spelled within the source code.
> For example:</p>
>
> <pre>
> - $ <b>g++-4.2 -fsyntax-only t.cpp</b>
> - t.cpp:12: error: no match for 'operator=' in 'str = vec'
> - $ <b>clang -fsyntax-only t.cpp</b>
> - t.cpp:12:7: <span class="err">error:</span> incompatible type assigning
> 'vector<Real>', expected 'std::string' (aka 'class
> std::basic_string<char>')
> + $ <span class="cmd">clang -fsyntax-only t.cpp</span>
> + <span class="loc">t.cpp:12:7:</span> <span class="err">error:</span>
> <span class="msg">incompatible type assigning 'vector<Real>',
> expected 'std::string' (aka 'class std::basic_string<char>')</span>
> <span class="snip">str = vec</span>;
> <span class="point">^ ~~~</span>
> </pre>
> @@ -237,14 +203,14 @@ code should be removed, then replaced wi
> point line (".x =" or ".y =", respectively).</p>
>
> <pre>
> - $ <b>clang t.c</b>
> - t.c:5:28: <span class="warn">warning:</span> use of GNU old-style field
> designator extension
> + $ <span class="cmd">clang t.c</span>
> + <span class="loc">t.c:5:28:</span> <span class="warn">warning:</span>
> <span class="msg">use of GNU old-style field designator extension</span>
> <span class="snip">struct point origin = { x: 0.0, y: 0.0 };</span>
> - <span class="err">~~</span> <span
> class="point">^</span>
> + <span class="err">~~</span> <span
> class="msg"><span class="point">^</span></span>
> <span class="snip">.x = </span>
> - t.c:5:36: <span class="warn">warning:</span> use of GNU old-style field
> designator extension
> + <span class="loc">t.c:5:36:</span> <span class="warn">warning:</span>
> <span class="msg">use of GNU old-style field designator extension</span>
> <span class="snip">struct point origin = { x: 0.0, y: 0.0 };</span>
> - <span class="err">~~</span> <span
> class="point">^</span>
> + <span class="err">~~</span> <span
> class="msg"><span class="point">^</span></span>
> <span class="snip">.y = </span>
> </pre>
>
> @@ -256,8 +222,8 @@ Clang provides the fix--add <code>templa
> diagnostic.<p>
>
> <pre>
> - $ <b>clang t.cpp</b>
> - t.cpp:9:3: <span class="err">error:</span> template specialization
> requires 'template<>'
> + $ <span class="cmd">clang t.cpp</span>
> + <span class="loc">t.cpp:9:3:</span> <span class="err">error:</span>
> <span class="msg">template specialization requires 'template<>'</span>
> struct iterator_traits<file_iterator> {
> <span class="point">^</span>
> <span class="snip">template<> </span>
> @@ -273,15 +239,15 @@ printed as an indented text tree.</p>
>
> Default: template diff with type elision
> <pre>
> -t.cc:4:5: <span class="note">note:</span> candidate function not viable:
> no known conversion from 'vector<map<[...], <span
> class="template-highlight">float</span>>>' to
> 'vector<map<[...], <span
> class="template-highlight">double</span>>>' for 1st argument;
> +<span class="loc">t.cc:4:5:</span> <span class="note">note:</span>
> candidate function not viable: no known conversion from
> 'vector<map<[...], <span
> class="template-highlight">float</span>>>' to
> 'vector<map<[...], <span
> class="template-highlight">double</span>>>' for 1st argument;
> </pre>
> -fno-elide-type: template diff without elision
> <pre>
> -t.cc:4:5: <span class="note">note:</span> candidate function not viable:
> no known conversion from 'vector<map<int, <span
> class="template-highlight">float</span>>>' to 'vector<map<int,
> <span class="template-highlight">double</span>>>' for 1st argument;
> +<span class="loc">t.cc:4:5:</span> <span class="note">note:</span>
> candidate function not viable: no known conversion from
> 'vector<map<int, <span
> class="template-highlight">float</span>>>' to 'vector<map<int,
> <span class="template-highlight">double</span>>>' for 1st argument;
> </pre>
> -fdiagnostics-show-template-tree: template tree printing with elision
> <pre>
> -t.cc:4:5: <span class="note">note:</span> candidate function not viable:
> no known conversion for 1st argument;
> +<span class="loc">t.cc:4:5:</span> <span class="note">note:</span>
> candidate function not viable: no known conversion for 1st argument;
> vector<
> map<
> [...],
> @@ -289,7 +255,7 @@ t.cc:4:5: <span class="note">note:</span
> </pre>
> -fdiagnostics-show-template-tree -fno-elide-type: template tree printing
> with no elision
> <pre>
> -t.cc:4:5: <span class="note">note:M</span> candidate function not viable:
> no known conversion for 1st argument;
> +<span class="loc">t.cc:4:5:</span> <span class="note">note:</span>
> candidate function not viable: no known conversion for 1st argument;
> vector<
> map<
> int,
> @@ -306,14 +272,11 @@ nested range information for diagnostics
> and also shows how some of the other pieces work in a bigger example.</p>
>
> <pre>
> - $ <b>gcc-4.2 -fsyntax-only t.c</b>
> - t.c: In function 'test':
> - t.c:80: error: invalid operands to binary < (have 'struct mystruct'
> and 'float')
> - $ <b>clang -fsyntax-only t.c</b>
> - t.c:80:3: <span class="err">error:</span> invalid operands to binary
> expression ('typeof(P)' (aka 'struct mystruct') and 'typeof(F)' (aka
> 'float'))
> + $ <span class="cmd">clang -fsyntax-only t.c</span>
> + <span class="loc">t.c:80:3:</span> <span class="err">error:</span>
> <span class="msg">invalid operands to binary expression ('typeof(P)' (aka
> 'struct mystruct') and 'typeof(F)' (aka 'float'))</span>
> <span class="snip"> X = MYMAX(P, F);</span>
> <span class="point"> ^~~~~~~~~~~</span>
> - t.c:76:94: note: expanded from:
> + <span class="loc">t.c:76:94:</span> <span class="note">note:</span>
> expanded from:
> <span class="snip">#define MYMAX(A,B) __extension__ ({ __typeof__(A)
> __a = (A); __typeof__(B) __b = (B); __a < __b ? __b : __a; })</span>
> <span class="point">
> ~~~ ^ ~~~</span>
> </pre>
> @@ -322,14 +285,14 @@ and also shows how some of the other pie
> implements the "wwopen" class of APIs):</p>
>
> <pre>
> - $ <b>clang -fsyntax-only t.c</b>
> - t.c:22:2: <span class="warn">warning:</span> type specifier missing,
> defaults to 'int'
> + $ <span class="cmd">clang -fsyntax-only t.c</span>
> + <span class="loc">t.c:22:2:</span> <span class="warn">warning:</span>
> <span class="msg">type specifier missing, defaults to 'int'</span>
> <span class="snip"> ILPAD();</span>
> <span class="point"> ^</span>
> - t.c:17:17: note: expanded from:
> + <span class="loc">t.c:17:17:</span> <span class="note">note:</span>
> expanded from:
> <span class="snip">#define ILPAD() PAD((NROW - tt.tt_row) * 10) /* 1
> ms per char */</span>
> <span class="point"> ^</span>
> - t.c:14:2: note: expanded from:
> + <span class="loc">t.c:14:2:</span> <span class="note">note:</span>
> expanded from:
> <span class="snip"> register i; \</span>
> <span class="point"> ^</span>
> </pre>
> @@ -342,63 +305,65 @@ macros that in simple ones.</p>
> <p>Finally, we have put a lot of work polishing the little things, because
> little things add up over time and contribute to a great user
> experience.</p>
>
> -<p>The following example shows a trivial little tweak, where we tell you
> to put the semicolon at
> -the end of the line that is missing it (line 4) instead of at the
> beginning of
> -the following line (line 5). This is particularly important with fixit
> hints
> -and point diagnostics, because otherwise you don't get the important
> context.
> -</p>
> -
> -<pre>
> - $ <b>gcc-4.2 t.c</b>
> - t.c: In function 'foo':
> - t.c:5: error: expected ';' before '}' token
> - $ <b>clang t.c</b>
> - t.c:4:8: <span class="err">error:</span> expected ';' after expression
> - <span class="snip"> bar()</span>
> - <span class="point"> ^</span>
> - <span class="point"> ;</span>
> -</pre>
> -
> -<p>The following example shows much better error recovery than GCC. The
> message coming out
> -of GCC is completely useless for diagnosing the problem. Clang tries much
> harder
> -and produces a much more useful diagnosis of the problem.</p>
> -
> -<pre>
> - $ <b>gcc-4.2 t.c</b>
> - t.c:3: error: expected '=', ',', ';', 'asm' or '__attribute__' before
> '*' token
> - $ <b>clang t.c</b>
> - t.c:3:1: <span class="err">error:</span> unknown type name 'foo_t'
> - <span class="snip">foo_t *P = 0;</span>
> - <span class="point">^</span>
> -</pre>
> -
> <p>The following example shows that we recover from the simple case of
> forgetting a ; after a struct definition much better than GCC.</p>
>
> <pre>
> - $ <b>cat t.cc</b>
> + $ <span class="cmd">cat t.cc</span>
> template<class T>
> - class a {}
> - class temp {};
> - a<temp> b;
> - struct b {
> + class a {};
> + struct b {}
> + a<int> c;
> + $ <span class="cmd">gcc-4.9 t.cc</span>
> + t.cc:4:8: error: invalid declarator before 'c'
> + a<int> c;
> + ^
> + $ <span class="cmd">clang t.cc</span>
> + <span class="loc">t.cc:3:12:</span> <span class="err">error:</span>
> <span class="msg">expected ';' after struct</span>
> + <span class="snip" >struct b {}</span>
> + <span class="point"> ^</span>
> + <span class="point"> ;</span>
> +</pre>
> +
> +<p>The following example shows that we diagnose and recover from a missing
> +<tt>typename</tt> keyword well, even in complex circumstances where GCC
> +cannot cope.</p>
> +
> +<pre>
> + $ <span class="cmd">cat t.cc</span>
> + template<class T> void f(T::type) { }
> + struct A { };
> + void g()
> + {
> + A a;
> + f<A>(a);
> }
> - $ <b>gcc-4.2 t.cc</b>
> - t.cc:3: error: multiple types in one declaration
> - t.cc:4: error: non-template type 'a' used as a template
> - t.cc:4: error: invalid type in declaration before ';' token
> - t.cc:6: error: expected unqualified-id at end of input
> - $ <b>clang t.cc</b>
> - t.cc:2:11: <span class="err">error:</span> expected ';' after class
> - <span class="snip">class a {}</span>
> - <span class="point"> ^</span>
> - <span class="point"> ;</span>
> - t.cc:6:2: <span class="err">error:</span> expected ';' after struct
> - <span class="snip">}</span>
> - <span class="point"> ^</span>
> - <span class="point"> ;</span>
> + $ <span class="cmd">gcc-4.9 t.cc</span>
> + t.cc:1:33: error: variable or field 'f' declared void
> + template<class T> void f(T::type) { }
> + ^
> + t.cc: In function 'void g()':
> + t.cc:6:5: error: 'f' was not declared in this scope
> + f<A>(a);
> + ^
> + t.cc:6:8: error: expected primary-expression before '>' token
> + f<A>(a);
> + ^
> + $ <span class="cmd">clang t.cc</span>
> + <span class="loc">t.cc:1:26:</span> <span class="error">error:</span>
> <span class="msg">missing 'typename' prior to dependent type name
> 'T::type'</span>
> + <span class="snip" >template<class T> void f(T::type) { }</span>
> + <span class="point"> ^~~~~~~</span>
> + <span class="point"> typename </span>
> + <span class="loc">t.cc:6:5:</span> <span class="error">error:</span>
> <span class="msg">no matching function for call to 'f'</span>
> + <span class="snip" > f<A>(a);</span>
> + <span class="point"> ^~~~</span>
> + <span class="loc">t.cc:1:24:</span> <span class="note">note:</span>
> <span class="msg">candidate template ignored: substitution failure [with T
> = A]: no type named 'type' in 'A'</span>
> + <span class="snip" >template<class T> void f(T::type) { }</span>
> + <span class="point"> ^ ~~~~</span>
> </pre>
>
> +
> +
> <p>While each of these details is minor, we feel that they all add up to
> provide
> a much more polished experience.</p>
>
>
>
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>
>
>
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