From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 28423 invoked by alias); 9 Aug 2002 16:56:01 -0000 Mailing-List: contact gcc-prs-help@gcc.gnu.org; run by ezmlm Precedence: bulk List-Archive: List-Post: List-Help: Sender: gcc-prs-owner@gcc.gnu.org Received: (qmail 28401 invoked by uid 71); 9 Aug 2002 16:56:01 -0000 Resent-Date: 9 Aug 2002 16:56:01 -0000 Resent-Message-ID: <20020809165601.28400.qmail@sources.redhat.com> Resent-From: gcc-gnats@gcc.gnu.org (GNATS Filer) Resent-To: nobody@gcc.gnu.org Resent-Cc: gcc-prs@gcc.gnu.org, gcc-bugs@gcc.gnu.org Resent-Reply-To: gcc-gnats@gcc.gnu.org, spencer@aol.net Received: (qmail 24351 invoked by uid 61); 9 Aug 2002 16:52:31 -0000 Message-Id: <20020809165231.24349.qmail@sources.redhat.com> Date: Fri, 09 Aug 2002 10:06:00 -0000 From: spencer@aol.net Reply-To: spencer@aol.net To: gcc-gnats@gcc.gnu.org X-Send-Pr-Version: gnatsweb-2.9.3 (1.1.1.1.2.31) Subject: optimization/7560: copy construction (return value optimization?) X-SW-Source: 2002-08/txt/msg00195.txt.bz2 List-Id: >Number: 7560 >Category: optimization >Synopsis: copy construction (return value optimization?) >Confidential: no >Severity: critical >Priority: medium >Responsible: unassigned >State: open >Class: wrong-code >Submitter-Id: net >Arrival-Date: Fri Aug 09 09:56:00 PDT 2002 >Closed-Date: >Last-Modified: >Originator: Brad Spencer >Release: gcc-3.1 and gcc-3.1.1 >Organization: >Environment: sparc64-sun-solaris2.8 >Description: I'm using both gcc-3.1 [cross and native] and gcc-3.1.1 [cross] for the sparc64-sun-solaris2.8 target. This bug only shows up when build 64-bit sparc targets AFAIK. starbug:/starbug/spencer$ /opt/gcc-3.1.1-cross/sparc64-sun-solaris2.8/bin/sparc64-sun-solaris2.8-g++ -v Reading specs from /opt/gcc-3.1.1-cross/sparc64-sun-solaris2.8/lib/gcc-lib/sparc64-sun-solaris2.8/3.1.1/specs Configured with: ../../gcc-3.1.1/configure --with-dwarf2 --enable-languages=c,c++ --enable-threads=single --disable-shared --prefix=/opt/gcc-3.1.1-cross/sparc64-sun-solaris2.8 --target=sparc64-sun-solaris2.8 -v --with-headers=/starbug/spencer/devel/gcc-cross/sparc64-sun-solaris2.8/target-stuff/include/ --with-lib=/opt/gcc-3.1.1-cross/sparc64-sun-solaris2.8/sparc64-sun-solaris2.8/lib --with-gnu-as --with-gnu-ld --disable-multilib Thread model: single gcc version 3.1.1 starbug:/starbug/spencer$ /opt/gcc-3.1-cross-sparc64-sun-solaris2.8/bin/sparc64-sun-solaris2.8-g++ -v Reading specs from /opt/gcc-3.1-cross-sparc64-sun-solaris2.8/lib/gcc-lib/sparc64-sun-solaris2.8/3.1/specs Configured with: ../gcc-3.1/configure --with-dwarf2 --enable-languages=c,c++ --enable-threads=single --disable-shared --prefix=/opt/gcc-3.1-cross-sparc64-sun-solaris2.8 --target=sparc64-sun-solaris2.8 -v --with-headers=/starbug/spencer/devel/gcc-cross/target-stuff/include/ --with-lib=/starbug/spencer/devel/gcc-cross/target-stuff/lib --with-gnu-as --with-gnu-ld --disable-multilib Thread model: single gcc version 3.1 netra-1:~$ /opt/gcc-3.1/bin/g++ -v Reading specs from /opt/gcc-3.1/lib/gcc-lib/sparc-sun-solaris2.8/3.1/specs Configured with: ../gcc-3.1/configure --with-dwarf2 --enable-languages=c,c++ --enable-threads=single --disable-shared --with-gnu-as --with-gnu-ld --with-as=/opt/bin/as --with-ld=/opt/bin/ld --prefix=/opt/gcc-3.1 Thread model: single gcc version 3.1 When running the following code compiled with any of these three compilers with optimizations on, the output is incorrect (see comments). What I suspect is happening is that the m_container member of Container::iterator is being treated as if it was only 32-bit during some optimization. Here is the code sample: +++BEGIN //***************************************************************************** // Shows bug when compiled with gcc-3.1 or gcc-3.1.1 at -O2 or higher for // sparc64-sun-solaris2.8. // // When compiled with -O or no optimizations, gives correct output: // /opt/gcc-3.1-cross-sparc64-sun-solaris2.8/bin/sparc64-sun-solaris2.8-g++ // -Wall -o optfoo optfoo.cc -O // *** begin: [0xffffffff7ffff9bf, 0, 0] end: [0xabcd, 123456, 1] // Not equal // // But when build with -O2 or higher, gives incorrect output: // /opt/gcc-3.1-cross-sparc64-sun-solaris2.8/bin/sparc64-sun-solaris2.8-g++ // -Wall -o optfoo optfoo.cc -O2 // *** begin: [0xffffffff7ffff9cf, 0, 0] end: [0xabcd, 0, 0] // equal // // Removing the const qualifier from the two const members of iterator also // avoids the bug, even on -O6: // /opt/gcc-3.1-cross-sparc64-sun-solaris2.8/bin/sparc64-sun-solaris2.8-g++ // -Wall -o optfoo optfoo.cc -O2 -DFOO_NO_CONST_MEMBERS // *** begin: [0xffffffff7ffff9cf, 0, 0] end: [0xabcd, 123456, 1] // Not equal #include #include #include // If FOO_NO_CONST_MEMBERS is set, then skip the const on the iterator members #if FOO_NO_CONST_MEMBERS # define DEBUG_CONST #else # define DEBUG_CONST const #endif //============================================================================= using std::cout; using std::endl; class Container { public: class iterator { // Not allowed void operator=(const iterator &); public: // creates as 'end' iterator() : m_container((Container *)0xABCD), m_all(true), m_idx(123456) {} bool operator!=(const iterator &rhs) const { return m_idx != rhs.m_idx; } // Return the packet itself const Container *getContainer() const { return m_container; } unsigned int getIdx() const { return m_idx; } bool getAll() const { return m_all; } protected: friend class Container; iterator(const Container *p,unsigned int i) : m_container(p), m_all(false), m_idx(i) {} explicit iterator(const Container *p) : m_container(p), m_all(true), m_idx(0) {} bool isValid() const { return m_container!=NULL; } private: const Container * DEBUG_CONST m_container; DEBUG_CONST bool m_all; unsigned int m_idx; }; iterator get() const { return iterator(this, 1); } iterator begin() const { return iterator(this, 0); } iterator end() const { return iterator(); } }; template class DirectSupportIterator : public Container::iterator, public std::iterator { private: // :: -------------------------------------------------------------------- // :: Type Information typedef Container::iterator BaseClass; public: // The value we dereference into typedef directly_supported_type value_type; public: // :: -------------------------------------------------------------------- // :: Construction // Copy construct from base class DirectSupportIterator(const BaseClass &it) : BaseClass(it) {} // Make "end" version DirectSupportIterator() : BaseClass() {} // Default copy and assignemnt }; typedef int SomeType; typedef DirectSupportIterator IteratorType; class Wrapper { Container p; public: IteratorType begin() const { return p.begin(); } static IteratorType end() { return IteratorType(); } }; int main() { std::ios::sync_with_stdio(false); Wrapper w; IteratorType begin = w.begin(); const IteratorType end = Wrapper::end(); cout << "*** begin: [" << begin.getContainer() << ", " << begin.getIdx() << ", " << begin.getAll() << "] end: [" << end.getContainer() << ", " << end.getIdx() << ", " << end.getAll() << ']' << std::endl; // Avoid logging if this field is not present if(begin != end) { cout << "Not equal" << endl; } else { cout << "equal" << endl; } return 0; } +++END [ - - - ] Here it is being built by gcc-3.1.1 (a cross compiler): starbug:/starbug/spencer$ /opt/gcc-3.1-cross-sparc64-sun-solaris2.8/bin/sparc64-sun-solaris2.8-g++ -Wall -o optfoo optfoo.cc -O2 -v Reading specs from /opt/gcc-3.1-cross-sparc64-sun-solaris2.8/lib/gcc-lib/sparc64-sun-solaris2.8/3.1/specs Configured with: ../gcc-3.1/configure --with-dwarf2 --enable-languages=c,c++ --enable-threads=single --disable-shared --prefix=/opt/gcc-3.1-cross-sparc64-sun-solaris2.8 --target=sparc64-sun-solaris2.8 -v --with-headers=/starbug/spencer/devel/gcc-cross/target-stuff/include/ --with-lib=/starbug/spencer/devel/gcc-cross/target-stuff/lib --with-gnu-as --with-gnu-ld --disable-multilib Thread model: single gcc version 3.1 /opt/gcc-3.1-cross-sparc64-sun-solaris2.8/lib/gcc-lib/sparc64-sun-solaris2.8/3.1/cc1plus -v -D__GNUC__=3 -D__GNUC_MINOR__=1 -D__GNUC_PATCHLEVEL__=0 -Dsparc -Dsun -Dunix -D__svr4__ -D__SVR4 -D__PRAGMA_REDEFINE_EXTNAME -D__sparc__ -D__sun__ -D__unix__ -D__svr4__ -D__SVR4 -D__PRAGMA_REDEFINE_EXTNAME -D__sparc -D__sun -D__unix -Asystem=unix -Asystem=svr4 -D__OPTIMIZE__ -D__STDC_HOSTED__=1 -D_XOPEN_SOURCE=500 -D_LARGEFILE_SOURCE=1 -D_LARGEFILE64_SOURCE=1 -D__EXTENSIONS__ -D__SIZE_TYPE__=long unsigned int -D__PTRDIFF_TYPE__=long int -D__WCHAR_TYPE__=int -D__WINT_TYPE__=int -D__arch64__ -Acpu=sparc64 -Amachine=sparcv9 -D__sparcv9 optfoo.cc -D__GNUG__=3 -D__DEPRECATED -D__EXCEPTIONS -D__GXX_ABI_VERSION=100 -quiet -dumpbase optfoo.cc -O2 -Wall -version -o /var/tmp//ccWZmCh0.s GNU CPP version 3.1 (cpplib) (sparc ELF) GNU C++ version 3.1 (sparc64-sun-solaris2.8) compiled by GNU C version 3.1. ignoring nonexistent directory "/opt/gcc-3.1-cross-sparc64-sun-solaris2.8/sparc64-sun-solaris2.8/include" #include "..." search starts here: #include <...> search starts here: /opt/gcc-3.1-cross-sparc64-sun-solaris2.8/include/g++-v3 /opt/gcc-3.1-cross-sparc64-sun-solaris2.8/include/g++-v3/sparc64-sun-solaris2.8 /opt/gcc-3.1-cross-sparc64-sun-solaris2.8/include/g++-v3/backward /opt/gcc-3.1-cross-sparc64-sun-solaris2.8/include /opt/gcc-3.1-cross-sparc64-sun-solaris2.8/lib/gcc-lib/sparc64-sun-solaris2.8/3.1/include /opt/gcc-3.1-cross-sparc64-sun-solaris2.8/sparc64-sun-solaris2.8/sys-include End of search list. /opt/gcc-3.1-cross-sparc64-sun-solaris2.8/lib/gcc-lib/sparc64-sun-solaris2.8/3.1/../../../../sparc64-sun-solaris2.8/bin/as -V -Qy -s -64 -Av9 -o /var/tmp//cc1scFwK.o /var/tmp//ccWZmCh0.s GNU assembler version 2.11.2 (sparc64-sun-solaris2.8) using BFD version 2.11.2 /opt/gcc-3.1-cross-sparc64-sun-solaris2.8/lib/gcc-lib/sparc64-sun-solaris2.8/3.1/collect2 -V -Y P,/usr/lib/sparcv9 -Qy -o optfoo /opt/gcc-3.1-cross-sparc64-sun-solaris2.8/lib/gcc-lib/sparc64-sun-solaris2.8/3.1/crt1.o /opt/gcc-3.1-cross-sparc64-sun-solaris2.8/lib/gcc-lib/sparc64-sun-solaris2.8/3.1/crti.o /usr/lib/sparcv9/values-Xa.o /opt/gcc-3.1-cross-sparc64-sun-solaris2.8/lib/gcc-lib/sparc64-sun-solaris2.8/3.1/crtbegin.o -L/opt/gcc-3.1-cross-sparc64-sun-solaris2.8/lib/gcc-lib/sparc64-sun-solaris2.8/3.1 -L/opt/gcc-3.1-cross-sparc64-sun-solaris2.8/lib/gcc-lib/sparc64-sun-solaris2.8/3.1/../../../../sparc64-sun-solaris2.8/lib /var/tmp//cc1scFwK.o -lstdc++ -lm -lgcc -lc -lgcc -lc /opt/gcc-3.1-cross-sparc64-sun-solaris2.8/lib/gcc-lib/sparc64-sun-solaris2.8/3.1/crtend.o /opt/gcc-3.1-cross-sparc64-sun-solaris2.8/lib/gcc-lib/sparc64-sun-solaris2.8/3.1/crtn.o GNU ld version 2.11.2 (with BFD 2.11.2) Supported emulations: elf64_sparc elf32_sparc [ - - - ] The expected output is of the form (the first pointer value is understandably different): netra-1:~$ /starbug/spencer/optfoo *** begin: [0xffffffff7ffff9cf, 0, 0] end: [0xabcd, 123456, 1] Not equal Here is a -O2 compiled version being run on a sparc64-sun-solaris2.8 box: netra-1:~$ /starbug/spencer/optfoo *** begin: [0xffffffff7ffff9cf, 0, 0] end: [0xabcd, 0, 0] equal The begin object is usually right during the failure, but the end object is always incorrect. As is suggested by the code comments, turning off -O2 or removing the two const qualifiers on Container::iterator's members avoids this bug. I suspect that this is the "return value optimization" acting up. I could not find a compiler option to turn off just this optimization. >How-To-Repeat: See description. >Fix: >Release-Note: >Audit-Trail: >Unformatted: