[oe] powerpc-g++ 4.2.4 problem casting long long to double
vjensen at gmx.de
Wed May 19 11:38:32 CEST 2010
We noticed a strange problem with C++ code casting long long variables to
double, as a lot of qt-embedded code is doing.
convert(long long l)
return (double)l; // or double(l)
main(int argc, char * argv)
long long l = 10;
f = convert(l);
printf("convert: %lld => %f\n", l, f);
convert: 10 => 0.000000
C++ compiled via powerpc-angstrom-linux-g++ gives the above result.
Compiling the same code as C using powerpc-angstrom-linux-gcc works fine.
But when looking at the assembler code both compiler produce virtually
identical output and both call __floatdidf to do the actual conversion.
Very strange, has anyone ever seen similar effects?
MACHINE bluepro (ppc603e, used in n1200, efika, lite5200, storcenter)
Openembedded is used to build images and QT4 SDKs for this machine which
work fine otherwise. The compiler version used is the default for
angstrom (4.2.4), that default and the gcc recipe is identical between
stable and dev branches.
ppc405 uses the older 4.1.1 gcc which shows the identical behaviour when
selected via ANGSTROM_GCC_VERSION. 4.3.2 and 4.3.3 failed to link but
created the same assembler code otherwise.
How can I analyse this situation further? I'm particular interested in
how different __floatdidf versions get used dependend on frontend, the
source of __floatdidf is in the gcc sourcetree and I expected it to be
compiled just once.
PS: fp-int-convert-long-double.c from the testsuite fails too, if
compiled via powerpc-angstrom-linux-g++
Vitus Jensen, Hannover, Germany, Universe (current)
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