const array initialisation (bug?)

[Pierangelo Masarati]

Hello.

This very simple program shows a different behaviour if compiled
with the gcc 2.91 coming with RedHat 6.2 (the expected one)
and with gcc 2.95.2 (the erroneous one?).

#include <iostream.h>
#include <math.h>

const double d1 = 1.;
const double dd1[2][1] = { { -d1 }, { d1 } };

const double d2 = (1.-sqrt(3.))/6.;
const double dd2[2][1] = { { -d2 }, { d2 } };
const double c = d2;

int main(void)
{
   cout
     << "d1 = " << d1
     << ", dd1 = {" << dd1[0][0] << "," << dd1[1][0] << "}" << endl
     << "d2 = " << d2 << ", c = " << c
     << ", dd2 = {" << dd2[0][0] << "," << dd2[1][0] << "}" << endl;
   return 0;
}

The expected behaviour, namely the constant array dd2 being correctly
initialised, has been obtained on different platforms. On the contrary,
gcc 2.95.2 does not initialise the array; this behaviour has been
obtained
both on a PC (RedHat Linux Box) and on a Digital Unix Alpha
(I can send the .ii and the log if required)
In case the expected behaviour is correct, this seems to be a bug; on
the
contrary, if this behaviour is erroneous, in my opinion the compiler
should at least warn that traditionally accepted behaviour is no longer
supported.

My regards, Pierangelo

Reading specs from
/usr/local/gcc-2.95.2/lib/gcc-lib/i686-pc-linux-gnu/2.95.2/specs
gcc version 2.95.2 19991024 (release)
 /usr/local/gcc-2.95.2/lib/gcc-lib/i686-pc-linux-gnu/2.95.2/cpp
-lang-c++ -v -D__GNUC__=2 -D__GNUG__=2 -D__GNUC_MINOR__=95 -D__cplusplus
-trigraphs -D__STRICT_ANSI__ -D__ELF__ -D__unix__ -D__i386__ -D__linux__
-D__unix -D__linux -Asystem(posix) -D__EXCEPTIONS -ggdb -Wall -W
-pedantic -Acpu(i386) -Amachine(i386) -D__i386 -D__i386__ -D__i686
-D__i686__ -D__pentiumpro -D__pentiumpro__ const.cc const.ii
GNU CPP version 2.95.2 19991024 (release) (i386 Linux/ELF)
#include "..." search starts here:
#include <...> search starts here:
 /usr/local/gcc-2.95.2/lib/gcc-lib/i686-pc-linux-gnu/2.95.2/include/g++
 /usr/local/include
 /usr/local/gcc-2.95.2/lib/gcc-lib/i686-pc-linux-gnu/2.95.2/../../../../i686-pc-linux-gnu/include

 /usr/local/gcc-2.95.2/lib/gcc-lib/i686-pc-linux-gnu/2.95.2/include
 /usr/include
End of search list.
The following default directories have been omitted from the search
path:
End of omitted list.
 /usr/local/gcc-2.95.2/lib/gcc-lib/i686-pc-linux-gnu/2.95.2/cc1plus
const.ii -quiet -dumpbase const.cc -ggdb -Wall -W -pedantic -ansi
-version -o const.s
GNU C++ version 2.95.2 19991024 (release) (i686-pc-linux-gnu) compiled
by GNU C version 2.95.2 19991024 (release).
 as -V -Qy -o const.o const.s
GNU assembler version 2.9.5 (i386-redhat-linux) using BFD version
2.9.5.0.22
 /usr/local/gcc-2.95.2/lib/gcc-lib/i686-pc-linux-gnu/2.95.2/collect2 -m
elf_i386 -dynamic-linker /lib/ld-linux.so.2 -o const /usr/lib/crt1.o
/usr/lib/crti.o
/usr/local/gcc-2.95.2/lib/gcc-lib/i686-pc-linux-gnu/2.95.2/crtbegin.o
-L/usr/local/gcc-2.95.2/lib/gcc-lib/i686-pc-linux-gnu/2.95.2
-L/usr/local/gcc-2.95.2/lib const.o -lstdc++ -lm -lgcc -lc -lgcc
/usr/local/gcc-2.95.2/lib/gcc-lib/i686-pc-linux-gnu/2.95.2/crtend.o
/usr/lib/crtn.o


--
Pierangelo Masarati, Ph.D.      | voice: ++39(02)2399-8365
Dip. Ing. Aerospaziale          | fax:   ++39(02)2399-8334
Politecnico di Milano           |
via La Masa 34, 20156 Italy     | mailto:masarati@aero.polimi.it
http://www.aero.polimi.it/personale/vari/masarati.htm


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