On 15/04/14 02:55, Unidata UDUNITS Support wrote:
Chris,
[I've driven your inquiry into our support-email system so that others can
benefit.]
Hi there,
Using master or d98f047 (v2.2.3), I ran into build problems. For some
reason libudunits2.so isn't build with -lm, causing the build of the
udunits2 bin to fail.
I belive the "-lm" option should be used when you build an application and not
when the UDUNITS sharable library is built.
My quick workaround was to rebuild the lib "manually" by appending "-lm" to
the original CC command.
You've likely just added the math library to the UDUNITS library. You can check
for this via the nm(1) utility.
My point is: The latest udunits doesn't build on ubuntu:
$ rm -Rf build && mkdir build && cd build
$ cmake ..
$ make
Scanning dependencies of target udunits2_doc
[ 5%] Built target udunits2_doc
Scanning dependencies of target libudunits2
[ 10%] Building C object lib/CMakeFiles/libudunits2.dir/converter.c.o
[ 15%] Building C object lib/CMakeFiles/libudunits2.dir/error.c.o
[ 21%] Building C object lib/CMakeFiles/libudunits2.dir/formatter.c.o
[ 26%] Building C object lib/CMakeFiles/libudunits2.dir/idToUnitMap.c.o
[ 31%] Building C object lib/CMakeFiles/libudunits2.dir/parser.c.o
[ 36%] Building C object lib/CMakeFiles/libudunits2.dir/prefix.c.o
[ 42%] Building C object lib/CMakeFiles/libudunits2.dir/status.c.o
[ 47%] Building C object lib/CMakeFiles/libudunits2.dir/systemMap.c.o
[ 52%] Building C object lib/CMakeFiles/libudunits2.dir/unitAndId.c.o
[ 57%] Building C object lib/CMakeFiles/libudunits2.dir/unitcore.c.o
[ 63%] Building C object lib/CMakeFiles/libudunits2.dir/unitToIdMap.c.o
[ 68%] Building C object lib/CMakeFiles/libudunits2.dir/ut_free_system.c.o
[ 73%] Building C object lib/CMakeFiles/libudunits2.dir/xml.c.o
Linking C shared library libudunits2.so
[ 84%] Built target libudunits2
Scanning dependencies of target udunits2lib_doc
[ 89%] Built target udunits2lib_doc
Scanning dependencies of target udunits2
[ 94%] Building C object prog/CMakeFiles/udunits2.dir/udunits2.c.o
Linking C executable udunits2
../lib/libudunits2.so: undefined reference to `fmod'
../lib/libudunits2.so: undefined reference to `exp'
../lib/libudunits2.so: undefined reference to `log'
../lib/libudunits2.so: undefined reference to `pow'
../lib/libudunits2.so: undefined reference to `log10'
../lib/libudunits2.so: undefined reference to `floor'
collect2: error: ld returned 1 exit status
make[2]: *** [prog/udunits2] Error 1
make[1]: *** [prog/CMakeFiles/udunits2.dir/all] Error 2
make: *** [all] Error 2
The only way to fix it is to tell gcc that libudunits depends on libm
while generating the .so:
Original command:
/usr/bin/cc -fPIC -shared -Wl,-soname,libudunits2.so -o
libudunits2.so [...] -lexpat
Fixed command:
/usr/bin/cc -fPIC -shared -Wl,-soname,libudunits2.so -o
libudunits2.so [...] -lexpat -lm
After the fix:
$ make
[ 5%] Built target udunits2_doc
[ 84%] Built target libudunits2
[ 89%] Built target udunits2lib_doc
Linking C executable udunits2
[ 94%] Built target udunits2
Scanning dependencies of target udunits2prog_doc
[100%] Built target udunits2prog_doc
Now i'm running into some basic usage problems, first the command line
test, which works:
$ echo $LC_NAME
en_NZ.UTF-8
$ udunits2
You have: 1e3 V.A
You want: W
1000 V.A = 1000 W
Now my quick test:
$ cat test.c
#include <stdio.h>
#include <udunits2.h>
int main(int argc, char *argv[])
{
ut_system *sys = ut_read_xml(NULL);
if (!sys) { printf("Sys error\n"); return 1; }
ut_unit *from = ut_parse(sys, "V.A", UT_UTF8);
if (!from) { printf("From error\n"); return 1; }
ut_unit *to = ut_parse(sys, "W", UT_UTF8);
if (!to) { printf("To error\n"); return 1; }
int res = ut_are_convertible(from, to);
if (res == 0) {
cv_converter* conv = ut_get_converter(from, to);
if (!conv) { printf("Conv error\n"); return 1; }
printf("%g\n", cv_convert_double(conv, 1e3));
}
else {
printf("%d %d %d\n", UT_SUCCESS, UT_NOT_SAME_SYSTEM, UT_BAD_ARG);
printf("%d %p %p\n", res, from, to);
}
The sense of the "res == 0" test in the above is inverted: the
function returns false (i.e., 0) if and only if numeric values are not
convertible between the two units.
My bad! Actually the documentation is clear enough on that point.
free(from);
free(to);
free(sys);
You should use ut_free(ut_unit*) and ut_free_system(ut_unit_system*)
in the above instead of free(). The documentation needs to be improved
in the area. I'll get on that.
My bad again, I think the documentation is clear enough.
return 0;
}
$ gcc -Wall test.c -o test -ludunits2 && ./test
0 5 1
1 0x9743b00 0x9748908
Which means that from and to are non null, but can_convert tells me that
one of the two is null (1=UT_BAD_ARG)
Am I doing something wrong? This is what the udunits2 command line tool is
doing basically
BTW, I have some warning messages as well (both with udunits2 -r and my
test prog):
[...]
The above warnings are expected for the reasons given. You can disable them.
Good, I think i will eventually customise my unit definitions.
Regards,
Steve Emmerson
Ticket Details
===================
Ticket ID: KIA-819973
Department: Support UDUNITS
Priority: Normal
Status: Closed
