../src/include/types_pub.h:88: error: conflicting declaration 'typedef int ISC_LONG'

Building Firebird 64bit on Solaris (sparc or intel) can sometimes produce the following error:
-c ../src/jrd/dsc.cpp -o ../temp/boot/jrd/dsc.o
../src/include/types_pub.h:88: error: conflicting declaration 'typedef int ISC_LONG'
../src/include/fb_types.h:69: error: 'ISC_LONG' has a previous declaration as 'typedef SLONG ISC_LONG'
../src/include/types_pub.h:89: error: conflicting declaration 'typedef unsigned int ISC_ULONG'
../src/include/fb_types.h:70: error: 'ISC_ULONG' has a previous declaration as 'typedef ULONG ISC_ULONG

If you see this - then you made a mistake in the build process. Configure.in when you invoked it, assumed that the size of long was 4, and you are attempting to build Firebird for a 32bit environment. As per the prefix.solaris files, you must set the following before running configure:

export CXXFLAGS='-m64'
export CFLAGS='-m64'
export LDFLAGS='-m64'

Configure will now automtically realise that you want to build in a 64 bit environment and set the size of long to 8.