GCC modified for the FreeChainXenon project
e3c898e12d
Implement C2x auto, a more restricted version of the C++ feature (closer to GNU C __auto_type in terms of what's supported). Since the feature is very close to GNU C __auto_type, much of the implementation can be shared. The main differences are: * Any prior declaration of the identifier in an outer scope is shadowed during the initializer (whereas __auto_type leaves any such declaration visible until the initializer ends and the scope of the __auto_type declaration itself starts). (A prior declaration in the same scope is undefined behavior.) * The standard feature supports braced initializers (containing a single expression, optionally followed by a comma). * The standard feature disallows the declaration from declaring anything that's not an ordinary identifier (thus, the initializer cannot declare a tag or the members of a structure or union), while making it undefined behavior for it to declare more than one ordinary identifier. (For the latter, while I keep the existing error from __auto_type in the case of more than one declarator, I don't restrict other ordinary identifiers from being declared in inner scopes such as GNU statement expressions. I do however disallow defining the members of an enumeration inside the initializer (if the enum definition has no tag, that doesn't actually violate a constraint), to avoid an enum type becoming accessible beyond where it would have been without auto. (Preventing new types from escaping the initializer - thus, ensuring that anything written with auto corresponds to something that could have been written without auto, modulo multiple evaluation of VLA size expressions when not using auto - is a key motivation for some restrictions on what can be declared in the initializer.) The rule on shadowing and restrictions on other declarations in the initializer are actually general rules for what C2x calls underspecified declarations, a description that covers constexpr as well as auto (in particular, this disallows a constexpr initializer from referencing the variable being initialized). Thus, some of the code added for those restrictions will also be of use in implementing C2x constexpr. auto with a type specifier remains a storage class specifier with the same meaning as before (i.e. a redundant storage class specifier for use at block scope). Note that the feature is only enabled in C2x mode (-std=c2x or -std=gnu2x); in older modes, a declaration with auto and no type is treated as a case of implicit int (only accepted at block scope). Since many of the restrictions on C2x auto are specified as undefined behavior rather than constraint violations, it would be possible to support more features from C++ auto without requiring diagnostics (but maybe not a good idea, if it isn't clear exactly what semantics might be given to such a feature in a future revision of C; and -Wc23-c2y-compat should arguably warn for any such future feature anyway). For now the features are limited to something close to what's supported with __auto_type, with the differences as discussed above between the two features. Bootstrapped with no regressions for x86_64-pc-linux-gnu. gcc/c/ * c-decl.cc (in_underspecified_init, start_underspecified_init) (finish_underspecified_init): New. (shadow_tag_warned, parser_xref_tag, start_struct, start_enum): Give errors inside initializers of underspecified declarations. (grokdeclarator): Handle (erroneous) case of C2X auto on a parameter. (declspecs_add_type): Handle c2x_auto_p case. (declspecs_add_scspec): Handle auto possibly setting c2x_auto_p in C2X mode. (finish_declspecs): Handle c2x_auto_p. * c-parser.cc (c_parser_declaration_or_fndef): Handle C2X auto. * c-tree.h (C_DECL_UNDERSPECIFIED): New macro. (struct c_declspecs): Add c2x_auto_p. (start_underspecified_init, finish_underspecified_init): New prototypes. * c-typeck.cc (build_external_ref): Give error for underspecified declaration referenced in its initializer. gcc/testsuite/ * gcc.dg/c2x-auto-1.c, gcc.dg/c2x-auto-2.c, gcc.dg/c2x-auto-3.c, gcc.dg/c2x-auto-4.c, gcc.dg/gnu2x-auto-1.c: New tests. |
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| c++tools | ||
| config | ||
| contrib | ||
| fixincludes | ||
| gcc | ||
| gnattools | ||
| gotools | ||
| include | ||
| INSTALL | ||
| intl | ||
| libada | ||
| libatomic | ||
| libbacktrace | ||
| libcc1 | ||
| libcody | ||
| libcpp | ||
| libdecnumber | ||
| libffi | ||
| libgcc | ||
| libgfortran | ||
| libgo | ||
| libgomp | ||
| 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 | ||
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