GCC modified for the FreeChainXenon project
969baf03ac
This new warning can be used to prevent expensive copies inside range-based
for-loops, for instance:
struct S { char arr[128]; };
void fn () {
S arr[5];
for (const auto x : arr) { }
}
where auto deduces to S and then we copy the big S in every iteration.
Using "const auto &x" would not incur such a copy. With this patch the
compiler will warn:
q.C:4:19: warning: loop variable 'x' creates a copy from type 'const S' [-Wrange-loop-construct]
4 | for (const auto x : arr) { }
| ^
q.C:4:19: note: use reference type 'const S&' to prevent copying
4 | for (const auto x : arr) { }
| ^
| &
As per Clang, this warning is suppressed for trivially copyable types
whose size does not exceed 64B. The tricky part of the patch was how
to figure out if using a reference would have prevented a copy. To
that point, I'm using the new function called ref_conv_binds_directly_p.
This warning is enabled by -Wall. Further warnings of similar nature
should follow soon.
gcc/c-family/ChangeLog:
PR c++/94695
* c.opt (Wrange-loop-construct): New option.
gcc/cp/ChangeLog:
PR c++/94695
* call.c (ref_conv_binds_directly_p): New function.
* cp-tree.h (ref_conv_binds_directly_p): Declare.
* parser.c (warn_for_range_copy): New function.
(cp_convert_range_for): Call it.
gcc/ChangeLog:
PR c++/94695
* doc/invoke.texi: Document -Wrange-loop-construct.
gcc/testsuite/ChangeLog:
PR c++/94695
* g++.dg/warn/Wrange-loop-construct.C: New test.
|
||
|---|---|---|
| config | ||
| contrib | ||
| fixincludes | ||
| gcc | ||
| gnattools | ||
| gotools | ||
| include | ||
| INSTALL | ||
| intl | ||
| libada | ||
| libatomic | ||
| libbacktrace | ||
| libcc1 | ||
| libcpp | ||
| libdecnumber | ||
| libffi | ||
| libgcc | ||
| libgfortran | ||
| libgo | ||
| libgomp | ||
| libhsail-rt | ||
| libiberty | ||
| libitm | ||
| libobjc | ||
| liboffloadmic | ||
| libphobos | ||
| libquadmath | ||
| libsanitizer | ||
| libssp | ||
| libstdc++-v3 | ||
| libvtv | ||
| lto-plugin | ||
| maintainer-scripts | ||
| zlib | ||
| .dir-locals.el | ||
| .gitattributes | ||
| .gitignore | ||
| ABOUT-NLS | ||
| ar-lib | ||
| ChangeLog | ||
| ChangeLog.jit | ||
| ChangeLog.tree-ssa | ||
| compile | ||
| config-ml.in | ||
| config.guess | ||
| config.rpath | ||
| config.sub | ||
| configure | ||
| configure.ac | ||
| COPYING | ||
| COPYING.LIB | ||
| COPYING.RUNTIME | ||
| COPYING3 | ||
| COPYING3.LIB | ||
| depcomp | ||
| install-sh | ||
| libtool-ldflags | ||
| libtool.m4 | ||
| ltgcc.m4 | ||
| ltmain.sh | ||
| ltoptions.m4 | ||
| ltsugar.m4 | ||
| ltversion.m4 | ||
| lt~obsolete.m4 | ||
| MAINTAINERS | ||
| Makefile.def | ||
| Makefile.in | ||
| Makefile.tpl | ||
| missing | ||
| mkdep | ||
| mkinstalldirs | ||
| move-if-change | ||
| multilib.am | ||
| README | ||
| symlink-tree | ||
| test-driver | ||
| ylwrap | ||
This directory contains the GNU Compiler Collection (GCC). The GNU Compiler Collection is free software. See the files whose names start with COPYING for copying permission. The manuals, and some of the runtime libraries, are under different terms; see the individual source files for details. The directory INSTALL contains copies of the installation information as HTML and plain text. The source of this information is gcc/doc/install.texi. The installation information includes details of what is included in the GCC sources and what files GCC installs. See the file gcc/doc/gcc.texi (together with other files that it includes) for usage and porting information. An online readable version of the manual is in the files gcc/doc/gcc.info*. See http://gcc.gnu.org/bugs/ for how to report bugs usefully. Copyright years on GCC source files may be listed using range notation, e.g., 1987-2012, indicating that every year in the range, inclusive, is a copyrightable year that could otherwise be listed individually.