[EDG eccp 3.9/Solaris 9] error on mkstemp() in file.cpp

The top of 4.2.0 fails to build with EDG eccp 3.9 on Solaris 9 with the error below:

$ nice gmake BUILDTYPE=11s BUILDDIR=/build/sebor/stdcxx-4.2.0-eccp-3.9-11s CONFIG=eccp.config
Bad string
creating BUILDDIR=/build/sebor/stdcxx-4.2.0-eccp-3.9-11s
generating /build/sebor/stdcxx-4.2.0-eccp-3.9-11s/makefile.in from /amd/homes/sebor/stdcxx-4.2.0/etc/config/eccp.config
Bad string
gmake[1]: Entering directory `/build/sebor/stdcxx-4.2.0-eccp-3.9-11s'
gmake[2]: Entering directory `/build/sebor/stdcxx-4.2.0-eccp-3.9-11s/include'
gmake config
gmake[3]: Entering directory `/build/sebor/stdcxx-4.2.0-eccp-3.9-11s/include'

configuring stdcxx 4.2.0 for eccp-3.9 on

checking if the compiler is sane ok (invoked with eccp)
checking if the linker is sane ok (invoked with eccp)
checking system architecture ILP32 big endian
...
eccp -c -I/amd/homes/sebor/stdcxx-4.2.0/include/ansi -D_RWSTDDEBUG -I/amd/homes/sebor/stdcxx-4.2.0/include -I/build/sebor/stdcxx-4.2.0-eccp-3.9-11s/include -A -x --template_directory=/build/sebor/stdcxx-4.2.0-eccp-3.9-11s/lib -g --display_error_number --remarks --diag_suppress 193,236,340,401,261,479,487,678,679,815 /amd/homes/sebor/stdcxx-4.2.0/src/file.cpp
"/amd/homes/sebor/stdcxx-4.2.0/src/file.cpp", line 265: error #20: identifier
"mkstemp" is undefined
fd = mkstemp (fnamebuf);
^

1 error detected in the compilation of "/amd/homes/sebor/stdcxx-4.2.0/src/file.cpp".
gmake[2]: *** [file.o] Error 2
gmake[2]: Leaving directory `/build/sebor/stdcxx-4.2.0-eccp-3.9-11s/lib'
gmake[1]: *** [lib] Error 2
gmake[1]: Leaving directory `/build/sebor/stdcxx-4.2.0-eccp-3.9-11s'
gmake: *** [libstd] Error 2