Flint content error for non-symbols in gcd_

[tueda]

Example:

CF f,x,y;
L F = gcd_(x+x*y,x-x*y);  * expected to be x
P;
.end

Result:

flint::gcd_mpoly: error: content of 1st arg != 1
Program terminating at test.frm Line 3 -->
Terminate called from /home/tueda/work/form/sources/flintinterface.cc:953 (gcd_
mpoly)
Backtrace:
# 0: TerminateImpl at startup.c:1936:16
# 1: _ZN5flint5mpolyD4Ev at flintinterface.h:108:35
  (inlined by) _ZN5flint9gcd_mpolyEPKiS1_iRKSt3mapIjjSt4lessIjESaISt4pairIKjjEE
E at flintinterface.cc:978:2
# 2: flint_gcd at flintwrap.cc:130:26
# 3: poly_gcd at polywrap.cc:128:24
# 4: GCDfunction3 at ratio.c:1204:12
# 5: GCDfunction at ratio.c:1059:7
# 6: Generator at proces.c:4045:9
# 7: Generator at proces.c:4078:18
# 8: Generator at proces.c:4078:18
# 9: Generator at proces.c:4246:8
#10: Processor at proces.c:409:11
#11: DoExecute at execute.c:859:24
#12: ExecModule at module.c:292:1
#13: PreProcessor at pre.c:1048:17
#14: main at startup.c:1815:2

Note that it gives the expected result x if Flint is turned off.

Version:

FORM 5.0.0 (Jan 27 2026, v5.0.0)
+backtrace  +flint=3.4.0  +gmp=6.3.0   -mpi    -pthreads  +zlib=1.3.1
+debugging  +float        +mpfr=4.2.2  +posix  -windows   +zstd=1.5.7
Compiler: GCC 15.2.0
Architecture: x86_64

[jodavies]

The flint interface is expecting content-free input which is composed only of symbols. If GCDfunction3 finds non-symbols in the input, it converts them to extrasymbols, but it seems it does not then remove the content: TakeContent is called before PutExtraSymbols but not after.

Edit: That said, it does look like TakeContent is also supposed to handle non-symbol objects, so presumably something goes wrong there.

The input for flint::gcd_mpoly is, as you might expect from the error, x1*x2+x2 and -x1*x2+x2.