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commit a886d546cbb54d071fe1bb83878bc7584de50800
Author: David Malcolm <[email protected]>
Date: Mon Mar 31 14:27:42 2025 -0400
My GCC 15 changes
diff --git a/htdocs/gcc-15/changes.html b/htdocs/gcc-15/changes.html
index 3e3c6655..1b7d0e1b 100644
--- a/htdocs/gcc-15/changes.html
+++ b/htdocs/gcc-15/changes.html
@@ -38,6 +38,15 @@ You may also want to check out our
padding bits is desirable, use <code>{}</code> (valid in C23 or C++)
or use <code>-fzero-init-padding-bits=unions</code> option to restore
old GCC behavior.</li>
+ <li><a
href="https://gcc.gnu.org/onlinedocs/gcc/Static-Analyzer-Options.html";><code>-fanalyzer</code></a>
+ is still only suitable for analyzing C code.
+ In particular, using it on C++ is unlikely to give meaningful output.
+ </li>
+ <li>The <code>json</code> format for
+ <a
href="https://gcc.gnu.org/onlinedocs/gcc/Diagnostic-Message-Formatting-Options.html#index-fdiagnostics-format";><code>-fdiagnostics-format=</code></a>
+ is deprecated and may be removed in a future release.
+ Users seeking machine-readable diagnostics from GCC should use
+ <a href="https://gcc.gnu.org/wiki/SARIF";>SARIF</a>.
</ul>
@@ -79,6 +88,20 @@ You may also want to check out our
significantly improved. The compiler can now track columnn numbers larger
than 4096. Very large source files have more accurate location reporting.
</li>
+ <li>GCC can now emit diagnostics in multiple formats simultaneously,
+ via the new option
+ <a
href="https://gcc.gnu.org/onlinedocs/gcc/Diagnostic-Message-Formatting-Options.html#index-fdiagnostics-add-output";><code>-fdiagnostics-add-output=</code></a>.
+ For example, use
+ <a
href="https://gcc.gnu.org/onlinedocs/gcc/Diagnostic-Message-Formatting-Options.html#index-fdiagnostics-add-output";><code>-fdiagnostics-add-output=sarif</code></a>
+ to get both GCC's classic text output on stderr <strong>and</strong>
+ <a href="https://gcc.gnu.org/wiki/SARIF";>SARIF</a> output to a file.
+ There is also a new option
+ <a
href="https://gcc.gnu.org/onlinedocs/gcc/Diagnostic-Message-Formatting-Options.html#index-fdiagnostics-set-output";><code>-fdiagnostics-set-output=</code></a>
+ which exposes more control than existing options for some experimental
cases.
+ These new options are an alternative to the existing
+ <a
href="https://gcc.gnu.org/onlinedocs/gcc/Diagnostic-Message-Formatting-Options.html#index-fdiagnostics-format";><code>-fdiagnostics-format=</code></a>
+ which only supports a single output format at a time.
+ </li>
</ul>
@@ -301,7 +324,7 @@ procedure Initialize (Obj : in out T);
New constraints have been added for defining symbols or using symbols
inside of inline assembler, and a new generic operand modifier has
been added to allow printing those regardless of PIC. For example:
-<pre>
+<pre><code>
struct S { int a, b, c; };
extern foo (void);
extern char var;
@@ -313,7 +336,7 @@ asm (".text; %cc0: mov %cc2, %%r0; .previous;"
"-s" (var2), /* Tell compiler asm uses var2 variable. */
/* "s" would work too but might not work with -fpic. */
"i" (sizeof (struct S))); /* It is possible to pass constants to toplevel
asm. */
-</pre>
+</code></pre>
</li>
<li>The <code>"redzone"</code> clobber is now allowed in inline
assembler statements to describe that the assembler can overwrite
@@ -333,6 +356,42 @@ asm (".text; %cc0: mov %cc2, %%r0; .previous;"
<code>-Wheader-guard</code></a> warning has been added and enabled
in <code>-Wall</code> to warn about some inconsistencies in header
file guarding macros.</li>
+ <li>The C and C++ frontends now provide fix-it hints for some cases of
missing
+ '<code>&</code>' and '<code>*</code>'.
+ For example, note the ampersand fix-it hint in the following:
+<pre><code>
+ demo.c: In function 'int main()':
+ demo.c:5:22: error: invalid conversion from 'pthread_key_t' {aka 'unsigned
int'}
+ to 'pthread_key_t*' {aka 'unsigned int*'} [-fpermissive]
+ 5 | pthread_key_create(key, NULL);
+ | ^~~
+ | |
+ | pthread_key_t {aka unsigned int}
+ demo.c:5:22: note: possible fix: take the address with '&'
+ 5 | pthread_key_create(key, NULL);
+ | ^~~
+ | &
+ In file included from demo.c:1:
+ /usr/include/pthread.h:1122:47: note: initializing argument 1 of
+ 'int pthread_key_create(pthread_key_t*, void (*)(void*))'
+ 1122 | extern int pthread_key_create (pthread_key_t *__key,
+ | ~~~~~~~~~~~~~~~^~~~~
+</code></pre>
+ </li>
+ <li>Diagnostic messages referring to attributes now provide URLs
+ to the documentation of the pertinent attributes in sufficiently
+ capable terminals, and in SARIF output.
+ </li>
+ <li>Diagnostics in which two different things in the source are
+ being contrasted (such as type mismatches) now use color to
+ visually highlight and distinguish the differences, in both the
+ text message of the diagnostic, and the quoted source. For example,
+ in:
+ <p><img src="diag-color-screenshot.png"
+ alt="screenshot of a C type error from GCC 15 showing color
usage"/></p>
+ the left-hand type is shown in green and the right-hand type in
+ dark blue.
+ </li>
</ul>
<h3 id="c">C</h3>
@@ -357,6 +416,10 @@ asm (".text; %cc0: mov %cc2, %%r0; .previous;"
<code>202311L</code>.</li>
</ul>
</li>
+ <li>To aid the transition to C23, various diagnostics have been enhanced
+ to clarify type errors such as incompatible function types, incorrect
+ argument counts, and those involving <code>bool</code>.
+ </li>
<li>Some new features from the upcoming C2Y revision of the ISO C
standard are supported with <code>-std=c2y</code>
and <code>-std=gnu2y</code>. Some of these features are also
@@ -555,7 +618,15 @@ asm (".text; %cc0: mov %cc2, %%r0; .previous;"
(<a
href="https://gcc.gnu.org/git/?p=gcc.git;a=commitdiff;h=12de1942a0a673f9f2f1c2bfce4279a666061ffc";>git</a>).
</li>
<li>
- Various diagnostic improvements.
+ A new way of presenting complicated diagnostics
+ (such as C++ template errors) is available via
+ <a
href="https://gcc.gnu.org/onlinedocs/gcc/Diagnostic-Message-Formatting-Options.html#index-fdiagnostics-set-output";><code>-fdiagnostics-set-output=text:experimental-nesting=yes</code></a>;
+ an example can be seen <a href="https://godbolt.org/z/K4jGrhao1";>here</a>.
+ This should be regarded as experimental in this release and is
+ subject to change.
+ </li>
+ <li>
+ Various other diagnostic improvements.
</li>
</ul>
<h4 id="libstdcxx">Runtime Library (libstdc++)</h4>
@@ -1215,12 +1286,195 @@ asm (".text; %cc0: mov %cc2, %%r0; .previous;"
<!-- .................................................................. -->
<!-- <h2>Documentation improvements</h2> -->
+<!-- .................................................................. -->
+<h2 id="sarif">Improvements to SARIF support</h2>
+<ul>
+ <li>GCC's <a href="https://gcc.gnu.org/wiki/SARIF";>SARIF</a> output has
+ been extended in the following ways
+ <ul>
+ <li>GCC's SARIF output now captures all locations and labelled
+ source ranges associated with a diagnostic, so that e.g. for
+ <pre><code>
+ PATH/missing-semicolon.c: In function 'missing_semicolon':
+ PATH/missing-semicolon.c:9:12: error: expected ';' before '}' token
+ 9 | return 42
+ | ^
+ | ;
+ 10 | }
+ | ~
+ </code></pre>
+ GCC's SARIF output now captures the secondary location (that of
+ the trailing close brace), as well as that of the missing
+ semicolon.
+ </li>
+ <li>For every location in a diagnostic that isn't in the main source
+ file, GCC's SARIF output now captures the chain of
+ <code>#include</code> directives that led to that location,
+ using <code>locationRelationship</code> objects
+ (<a
href="https://docs.oasis-open.org/sarif/sarif/v2.1.0/errata01/os/sarif-v2.1.0-errata01-os-complete.html#_Toc141790978";>§3.34</a>).
+ </li>
+ <li>SARIF <a
href="https://docs.oasis-open.org/sarif/sarif/v2.1.0/errata01/os/sarif-v2.1.0-errata01-os-complete.html#_Toc141790709";><code>message</code></a>
+ objects now capture embedded URLs in GCC diagnostics
+ (<a
href="https://docs.oasis-open.org/sarif/sarif/v2.1.0/errata01/os/sarif-v2.1.0-errata01-os-complete.html#_Toc141790717";>§3.11.6</a>).
+ In particular, references to other events in diagnostic paths now
+ capture URLs to the pertinent <code>threadFlowLocation</code> object
+ for the other event, such as
+ <pre><code>
+ "text": "second 'free' here; first 'free' was at
[(1)](sarif:/runs/0/results/0/codeFlows/0/threadFlows/0/locations/0)"
+ </code></pre>
+ </li>
+ <li>GCC's SARIF output now captures the command-line arguments
+ (<a
href="https://docs.oasis-open.org/sarif/sarif/v2.1.0/errata01/os/sarif-v2.1.0-errata01-os-complete.html#_Toc141790819";>§3.20.2</a>),
+ timestamps for the start and end of compilation
+ (<a
href="https://docs.oasis-open.org/sarif/sarif/v2.1.0/errata01/os/sarif-v2.1.0-errata01-os-complete.html#_Toc141790824";>§§3.20.7-8</a>),
+ and the working directory
+ (<a
href="https://docs.oasis-open.org/sarif/sarif/v2.1.0/errata01/os/sarif-v2.1.0-errata01-os-complete.html#_Toc141790836";>§3.20.19</a>).
+ It also now sets the <code>roles</code> property for SARIF
+ <code>artifact</code> objects
+ (<a
href="https://docs.oasis-open.org/sarif/sarif/v2.1.0/errata01/os/sarif-v2.1.0-errata01-os-complete.html#_Toc141790867";>§3.24.6</a>).
+ </li>
+ <li>For warnings where encoding is significant, such as
+ <a
href="https://gcc.gnu.org/onlinedocs/gcc/Warning-Options.html#index-Wbidi-chars";>-Wbidi-chars</a>
+ for a "trojan source" attack GCC's SARIF output gains a
+ <code>rendered</code> property
+ (<a
href="https://docs.oasis-open.org/sarif/sarif/v2.1.0/errata01/os/sarif-v2.1.0-errata01-os-complete.html#_Toc141790676";>§3.3.4</a>)
+ that escapes non-ASCII text in source snippets, such as:
+ <pre><code>
+ "rendered": {"text":
+ </code></pre>
+ where "text" has a string value such as:
+ <pre><code>
+ "22 | /* end admins only <U+202E> {{ <U+2066>:*/\n"
+ " | ~~~~~~~~ ~~~~~~~~ ^\n"
+ " | | | |\n"
+ " | | | end of
bidirectional context\n"
+ " | | U+2066 (LEFT-TO-RIGHT
ISOLATE)\n"
+ " | U+202E (RIGHT-TO-LEFT
OVERRIDE)\n"}}}},
+ </code></pre>
+ (shown here with the JSON string split into multiple lines
+ for clarity).
+ </li>
+ <li>Experimental SARIF 2.2 output has been added, via
+ <a
href="https://gcc.gnu.org/onlinedocs/gcc/Diagnostic-Message-Formatting-Options.html#index-fdiagnostics-add-output";><code>-fdiagnostics-add-output=sarif:version=2.2-prerelease</code></a>.
+ Given that the SARIF 2.2 specification is still under development, this
+ uses an unofficial draft of the specification, and is subject to change.
+ </li>
+ <li>The crash handler has been extended so that it will attempt to
+ capture a backtrace of GCC's stack in JSON form within a property bag
+ in SARIF output. The precise format of the property is subject to
change
+ </li>
+ </ul>
+ <li>GCC 15 adds a new <code>sarif-replay</code> command-line tool for
+ <strong>viewing</strong> <code>.sarif</code> files. It uses
+ <a href="https://gcc.gnu.org/wiki/libgdiagnostics";>libgdiagnostics</a>
+ to "replay" any diagnostics found in the <code>.sarif</code> files in
+ text form as if they were GCC diagnostics, with support for details such
+ as fix-it hints, underlined ranges, and diagnostic paths.
+ </li>
+</ul>
+
<!-- .................................................................. -->
<!-- <h2 id="plugins">Improvements for plugin authors</h2> -->
+<!-- .................................................................. -->
+<h2 id="analyzer">Improvements to Static Analyzer</h2>
+<ul>
+ <li>GCC's logic for printing execution paths has been improved
+ in various ways
+ <ul>
+ <li>The problematic event in an analyzer path is now highlighted with
+ a warning emoji (â ï¸), where the locale supports this, such as in the
+ examples below.
+ </li>
+ <li>Paths can show control flow using ASCII art, such as:
+ <pre><code>
+infinite-loop-linked-list.c: In function âwhile_loop_missing_nextâ:
+infinite-loop-linked-list.c:30:10: warning: infinite loop [CWE-835]
[-Wanalyzer-infinite-loop]
+ 30 | while (n)
+ | ^
+ âwhile_loop_missing_nextâ: events 1-3
+ 30 | while (n)
+ | ^
+ | |
+ | (1) â ï¸ infinite loop here
+ | (2) when ânâ is non-NULL: always following âtrueâ
branch... â>ââ
+ |
â
+ |
â
+
|ââââââââââââââââââââââââââââââââââââââââââââââââââââââââââââââââââââââââââ
+ 31 |â {
+ 32 |â sum += n->val;
+ |â ~~~~~~
+ |â |
+ |ââââââââââââââ>(3) ...to here
+ âwhile_loop_missing_nextâ: event 4
+ 32 | sum += n->val;
+ | ~~~~^~~~~~~~~
+ | |
+ | (4) looping back... â>ââ
+ | â
+ âwhile_loop_missing_nextâ: event 5
+ | â
+
|âââââââââââââââââââââââââââââââââââ
+ 30 |â while (n)
+ |â ^
+ |â |
+ |âââââââââ>(5) ...to here
+ </code></pre>
+ </li>
+ <li>Interprocedural depth markers now use unicode box-drawing
+ characters where the locale supports this, and they are eliminated
+ for purely intraprocedural paths, such as in the example of
+ <a
href="https://gcc.gnu.org/onlinedocs/gcc/Static-Analyzer-Options.html#index-Wanalyzer-infinite-loop";><code>-Wanalyzer-infinite-loop</code></a>
+ above.
+ </li>
+ </ul>
+ </li>
+ <li>
+ A new
+ <a
href="https://gcc.gnu.org/onlinedocs/gcc/Static-Analyzer-Options.html";><code>-fanalyzer</code></a>
+ warning
+ <a
href="https://gcc.gnu.org/onlinedocs/gcc/Static-Analyzer-Options.html#index-Wanalyzer-undefined-behavior-ptrdiff";><code>-Wanalyzer-undefined-behavior-ptrdiff</code></a>
+ warns about pointer subtractions involving different chunks of memory.
+ For example:
+ <pre><code>
+ demo.c: In function âtest_invalid_calc_of_array_sizeâ:
+ demo.c:9:20: warning: undefined behavior when subtracting pointers
[CWE-469] [-Wanalyzer-undefined-behavior-ptrdiff]
+ 9 | return &sentinel - arr;
+ | ^
+ events 1-2
+ â
+ â 3 | int arr[42];
+ â | ~~~
+ â | |
+ â | (2) underlying object for right-hand side of
subtraction created here
+ â 4 | int sentinel;
+ â | ^~~~~~~~
+ â | |
+ â | (1) underlying object for left-hand side of subtraction
created here
+ â
+ âââ> âtest_invalid_calc_of_array_sizeâ: event 3
+ â
+ â 9 | return &sentinel - arr;
+ â | ^
+ â | |
+ â | (3) â ï¸ subtraction of
pointers has undefined behavior if they do not point into the same array object
+ â
+ </code></pre>
+ </li>
+</ul>
+
<!-- .................................................................. -->
<h2>Other significant improvements</h2>
+<h3 id="libgdiagnostics">libgdiagnostics</h3>
+<p>GCC's code for emitting diagnostics is now available to other
+ GPL3-compatible projects as a shared library,
+ <a href="https://gcc.gnu.org/wiki/libgdiagnostics";>libgdiagnostics</a>.
+ This covers such features as colorization, quoting lines of source code,
+ labelling ranges of source, fix-it hints, execution paths, SARIF output,
+ and so on.
+ There is a C API, along with C++ and Python bindings.</p>
+
<!-- <h3 id="uninitialized">Eliminating uninitialized variables</h3> -->
<!-- .................................................................. -->
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