Modern C++ (i.e., C++11 and later) introduced "move only" types: types such
as std::unique_ptr<T> that can never be duplicated. They must never be
copied (by assignments and constructors), they must be "moved". The
implementation of lalr1.cc used to copy symbols (including their semantic
values). This commit ensures that values are only moved in modern C++, yet
remain compatible with C++98/C++03.
Suggested by Frank Heckenbach, who provided a full implementation on
top of C++17's std::variant.
See http://lists.gnu.org/archive/html/bug-bison/2018-03/msg00002.html,
and https://lists.gnu.org/archive/html/bison-patches/2018-04/msg00002.html.
Symbols (terminal/non terminal) are handled by several functions that used
to take const-refs, which resulted eventually in a copy pushed on the stack.
With modern C++ (C++11 and later) the callers must use std::move, and the
callees must take their arguments as rvalue refs (foo&&). In order to avoid
duplicating these functions to support both legacy C++ and modern C++, let's
introduce macros (YY_MOVE, YY_RVREF, etc.) that rely on copy-semantics for
C++98/03, and move-semantics for modern C++.
That's easy for inner types, when the parser's functions pass arguments to
each other. Functions facing the user (make_NUMBER, make_STRING, etc.)
should support both rvalue-refs (for instance to support move-only types:
make_INT (std::make_unique<int> (1))), and lvalue-refs (so that we can pass
a variable: make_INT (my_int)). To avoid the multiplication of the
signatures (there is also the location), let's take the argument by value.
See:
https://lists.gnu.org/archive/html/bison-patches/2018-09/msg00024.html.
* data/c++.m4 (b4_cxx_portability): New.
(basic_symbol): In C++11, replace copy-ctors with move-ctors.
In C++11, replace copies with moves.
* data/lalr1.cc (stack_symbol_type, yypush_): Likewise.
Use YY_MOVE to avoid useless copies.
* data/variant.hh (variant): Support move-semantics.
(make_SYMBOL): In C++11, in order to support both read-only lvalues,
and rvalues, take the argument as a copy.
* data/stack.hh (yypush_): Use rvalue-refs in C++11.
* tests/c++.at: Use move semantics.
* tests/headers.at: Adjust to the new macros (YY_MOVE, etc.).
* configure.ac (CXX98_CXXFLAGS, CXX11_CXXFLAGS, CXX14_CXXFLAGS)
(CXX17_CXXFLAGS, ENABLE_CXX11): New.
* tests/atlocal.in: Receive them.
* examples/variant.yy: Don't define things in std.
* examples/variant-11.test, examples/variant-11.yy: New.
Check the support of move-only types.
* examples/README, examples/local.mk: Adjust.
With GCC7 we have warnings (false positive):
x8.c: In function 'x8_parse':
x8.c:1233:16: error: 'yylval' may be used uninitialized in this function [-Werror=maybe-uninitialized]
yylval = *yypushed_val;
~~~~~~~^~~~~~~~~~~~~~~
x8.c: In function 'x8_pull_parse':
x8.c:1233:16: error: 'yylval' may be used uninitialized in this function [-Werror=maybe-uninitialized]
yylval = *yypushed_val;
~~~~~~~^~~~~~~~~~~~~~~
See also 9645a2b20e.
* tests/local.at (AT_PUSH_IF): New.
(AT_BISON_OPTION_POPDEFS): Pop it, and pop AT_PURE_IF.
* tests/headers.at (Several parsers, Several parsers): Disable these
warnings when in push parser.
The header generated for variants with assertions but without
locations, is not self-contained. Prepare a check for this.
* tests/headers.at (Sane headers): New, extracted from...
(Several parsers): here.
* data/lalr1.cc, doc/bison.texi, etc/bench.pl.in, examples/variant.yy,
* tests/actions.at, tests/atlocal.in, tests/c++.at, tests/headers.at,
* tests/local.at, tests/types.at:
Don't use std::endl, it flushes uselessly, and is considered bad
style.
Building C++ parsers with -Wsuggest-attribute=const and
-Wsuggest-attribute=noreturn triggers warning in generated code.
* data/lalr1.cc: Call b4_attribute_define.
(debug_stream, debug_level): Flag as pure.
* tests/headers.at (Several parsers): There are now more YY macros
that "leak".
* tests/local.at (AT_NAME_PREFIX): Also match api.namespace.
(AT_MAIN_DEFINE): Take it into account.
* tests/c++.at, tests/headers.at: Use AT_NAME_PREFIX.
(AT_CHECK_NAMESPACE): Rename as...
(AT_TEST): this.
Reported by Théophile Ranquet.
* tests/glr-regression.at: Rewrite some test cases so that AT_PARSER_CHECK,
which runs valgrind, is exposed with the parser, not with "echo".
* tests/local.at, tests/regression.at, tests/headers.at:
Use AT_PARSER_CHECK for generated parsers.
Does not work on Solaris 10. Reported by Dennis Clarke.
http://lists.gnu.org/archive/html/bug-bison/2012-11/msg00009.html
* tests/headers.at (Several parsers): Use Perl instead.
While at it, run it only once, on all the generated headers.
Adjust to YY_NULL be defined in position.hh.
Reported by Rob Vermaas' Hydra build farm on x86_64-darwin 10.2.0 with
G++ 4.6.3.
* tests/headers.at (Several parsers): Include AT_DATA_SOURCE_PROLOGUE
in the files to compile.
* data/location.cc: Do not include twice string and iostream (once
by position.hh, and then by location.hh).
* README-hacking (Typical errors): Some hints for other maintainers.
Reported by Rob Vermaas' Hydra build farm on x86_64-darwin 10.2.0 with
G++ 4.6.3.
* tests/headers.at (Several parsers): Include AT_DATA_SOURCE_PROLOGUE
in the files to compile.
* data/location.cc: Do not include twice string and iostream (once
by position.hh, and then by location.hh).
* README-hacking (Typical errors): Some hints for other maintainers.
* tests/local.at (AT_COMPILE, AT_COMPILE_CXX): If OUTPUT ends with ".o",
then append the "natural" extension for the input file (.c or .cc).
If there is no source, pass -c.
* tests/headers.at, tests/input.at, tests/regression.at: Adjust.
starting at
<http://lists.gnu.org/archive/html/bison-patches/2007-11/msg00021.html>.
* configure.ac (XSLTPROC): New substitution.
* Makefile.am (maintainer-xml-check): New phony target invoking...
* tests/Makefile.am (maintainer-xml-check): ... this new phony target
invoking make maintainer-check with BISON_TEST_XML=1.
* tests/atlocal.in (XSLTPROC): New.
* tests/local.at (AT_BISON_CHECK): New macro to (1) instruct Valgrind
not to report reachable memory when Bison is expected to have a
non-zero exit status and (2) to compare XML/XSLT output with --graph
and --report=all output for every working grammar when
BISON_TEST_XML=1.
(AT_BISON_CHECK_NO_XML): Likewise, but skip XML checks.
(AT_BISON_CHECK_XML): New.
(AT_QUELL_VALGRIND): New.
* tests/testsuite.at (ORIGINAL_AT_CHECK): Remove this and...
(AT_CHECK): ... don't redefine this since this was the old way to
quell Valgrind.
* tests/actions.at: Rewrite all AT_CHECK invocations for bison as
AT_BISON_CHECK invocations.
* tests/c++.at: Likewise.
* tests/calc.at: Likewise.
* tests/conflicts.at: Likewise.
* tests/cxx-type.at: Likewise.
* tests/existing.at: Likewise.
* tests/glr-regression.at: Likewise.
* tests/headers.at: Likewise.
* tests/input.at: Likewise.
* tests/java.at: Likewise.
* tests/output.at: Likewise.
* tests/push.at: Likewise.
* tests/reduce.at: Likewise.
* tests/regression.at: Likewise.
* tests/sets.at: Likewise.
* tests/skeletons.at: Likewise.
* tests/synclines.at: Likewise.
* tests/torture.at: Likewise.
(Big triangle): Use AT_BISON_CHECK_NO_XML instead since this grammar
tends to hang xsltproc.
(Big horizontal): Likewise.
(whether successful or failed) so that yypush_parse can be invoked
again to start a new parse using the same yypstate.
* tests/torture.at (AT_DATA_STACK_TORTURE): For push mode, extend to
check multiple yypull_parse invocations on the same yypstate. For pull
mode, extend to check multiple yyparse invocations.
(Exploding the Stack Size with Alloca): Extend to try with
%push-pull-parser.
(Exploding the Stack Size with Malloc): Likewise.
* tests/calc.at (Simple LALR Calculator): Don't specify
%skeleton "push.c" since %push-pull-parser implies that now.
* tests/headers.at (export YYLTYPE): Don't check for the push
declarations. Otherwise, this test case can't be used to see if push
mode can truly emulate pull mode.
* tests/input.at (Torturing the Scanner): Likewise.
* tests/local.at (AT_YACC_OR_PUSH_IF, AT_PUSH_IF): Remove.
(AT_YYERROR_SEES_LOC_IF): Rather than AT_YACC_OR_PUSH_IF, use
AT_YACC_IF, which now includes the case of push mode since %skeleton
need not be used for push mode. This will be more intuitive once
push.c is renamed to yacc.c.
