According to the 6.1.3.5 [tr.tuple.rel], there is an implicit dependencies on the sizes of the tuples being compared, and there should be a compilation failure if the tuples are not the same size.
However I am not seeing compilation errors in this case. The following example compiles and runs. Below that is the output from compilation with " g++ -v -save-temps". #include <tr1/tuple> int main() { std::tr1::tuple<int> t1( 1 ); std::tr1::tuple<int, int> t2( 1, 2 ); if ( t1 < t2 ) {} if ( t1 == t2 ) {} } 1$ g++ -v -save-temps tuples.cpp Using built-in specs. Target: i486-linux-gnu Configured with: ../src/configure -v --enable-languages=c,c++,fortran,objc,obj-c++,treelang --prefix=/usr --enable-shared --with-system-zlib --libexecdir=/usr/lib --without-included-gettext --enable-threads=posix --enable-nls --with-gxx-include-dir=/usr/include/c++/4.1.3 --program-suffix=-4.1 --enable-__cxa_atexit --enable-clocale=gnu --enable-libstdcxx-debug --enable-mpfr --enable-checking=release i486-linux-gnu Thread model: posix gcc version 4.1.3 20070929 (prerelease) (Ubuntu 4.1.2-16ubuntu2) /usr/lib/gcc/i486-linux-gnu/4.1.3/cc1plus -E -quiet -v -D_GNU_SOURCE tuples.cpp -mtune=generic -fpch-preprocess -o tuples.ii ignoring nonexistent directory "/usr/local/include/i486-linux-gnu" ignoring nonexistent directory "/usr/lib/gcc/i486-linux-gnu/4.1.3/../../../../i486-linux-gnu/include" ignoring nonexistent directory "/usr/include/i486-linux-gnu" #include "..." search starts here: #include <...> search starts here: /usr/include/c++/4.1.3 /usr/include/c++/4.1.3/i486-linux-gnu /usr/include/c++/4.1.3/backward /usr/local/include /usr/lib/gcc/i486-linux-gnu/4.1.3/include /usr/include End of search list. /usr/lib/gcc/i486-linux-gnu/4.1.3/cc1plus -fpreprocessed tuples.ii -quiet -dumpbase tuples.cpp -mtune=generic -auxbase tuples -version -fstack-protector -fstack-protector -o tuples.s GNU C++ version 4.1.3 20070929 (prerelease) (Ubuntu 4.1.2-16ubuntu2) (i486-linux-gnu) compiled by GNU C version 4.1.3 20070929 (prerelease) (Ubuntu 4.1.2-16ubuntu2). GGC heuristics: --param ggc-min-expand=100 --param ggc-min-heapsize=131072 Compiler executable checksum: 3cc47be363985179cfafdceddd0e8f5d as --traditional-format -V -Qy -o tuples.o tuples.s GNU assembler version 2.18 (i486-linux-gnu) using BFD version (GNU Binutils for Ubuntu) 2.18 /usr/lib/gcc/i486-linux-gnu/4.1.3/collect2 --eh-frame-hdr -m elf_i386 --hash-style=both -dynamic-linker /lib/ld-linux.so.2 /usr/lib/gcc/i486-linux-gnu/4.1.3/../../../../lib/crt1.o /usr/lib/gcc/i486-linux-gnu/4.1.3/../../../../lib/crti.o /usr/lib/gcc/i486-linux-gnu/4.1.3/crtbegin.o -L/usr/lib/gcc/i486-linux-gnu/4.1.3 -L/usr/lib/gcc/i486-linux-gnu/4.1.3 -L/usr/lib/gcc/i486-linux-gnu/4.1.3/../../../../lib -L/lib/../lib -L/usr/lib/../lib tuples.o -lstdc++ -lm -lgcc_s -lgcc -lc -lgcc_s -lgcc /usr/lib/gcc/i486-linux-gnu/4.1.3/crtend.o /usr/lib/gcc/i486-linux-gnu/4.1.3/../../../../lib/crtn.o -- Summary: Relational operators for <tr1/tuple> don't error on different sized tuples Product: gcc Version: 4.3.1 Status: UNCONFIRMED Severity: normal Priority: P3 Component: c++ AssignedTo: unassigned at gcc dot gnu dot org ReportedBy: gryan at akoostix dot com http://gcc.gnu.org/bugzilla/show_bug.cgi?id=35480