CLISP - an ANSI Common Lisp

thank you for your bug report.
the bug has been fixed in the CVS tree.
you can either wait for the next release (recommended)
or check out the current CVS tree (see http://clisp.cons.org)
and build CLISP from the sources (be advised that between
releases the CVS tree is very unstable and may not even build
on your platform).

specifically,
DEFCHECKER(check_lockmode, enum=db_lockmode_t, prefix=DB_LOCK, default=,
\
NG READ WRITE WAIT IWRITE IREAD IWR DIRTY WWRITE)
is transformed into
...
static const c_lisp_pair_t check_lockmode_table[] = {
{ DB_LOCK_NG, &(O(object_Kng)) },
{ DB_LOCK_READ, &(O(object_Kread)) },
{ DB_LOCK_WRITE, &(O(object_Kwrite)) },
{ DB_LOCK_WAIT, &(O(object_Kwait)) },
{ DB_LOCK_IWRITE, &(O(object_Kiwrite)) },
{ DB_LOCK_IREAD, &(O(object_Kiread)) },
{ DB_LOCK_IWR, &(O(object_Kiwr)) },
{ DB_LOCK_DIRTY, &(O(object_Kdirty)) },
{ DB_LOCK_WWRITE, &(O(object_Kwwrite)) },
{ 0, NULL }
};
...
normally, an ifdef would guard each line like this:
...
#ifdef DB_NEXT
{ DB_NEXT, &(O(object_Knext)) },
#endif
...
but in this particular case the constants DB_LOCK_* are not #defined,
they are enumerated in /usr/include/db4/db.h:
...
/*
* Simple R/W lock modes and for multi-granularity intention locking.
*
* !!!
* These values are NOT random, as they are used as an index into the
lock
* conflicts arrays, i.e., DB_LOCK_IWRITE must be == 3, and DB_LOCK_IREAD
* must be == 4.
*/
typedef enum {
DB_LOCK_NG=0, /* Not granted. */
DB_LOCK_READ=1, /* Shared/read. */
DB_LOCK_WRITE=2, /* Exclusive/write. */
DB_LOCK_WAIT=3, /* Wait for event */
DB_LOCK_IWRITE=4, /* Intent exclusive/write. */
DB_LOCK_IREAD=5, /* Intent to share/read. */
DB_LOCK_IWR=6, /* Intent to read and write. */
DB_LOCK_DIRTY=7, /* Dirty Read. */
DB_LOCK_WWRITE=8 /* Was Written. */
} db_lockmode_t;
...
so there is no way (except for a configure trick) to find out if a
specific constant is present.
Normally, developers would do something like (/usr/include/sys/socket.h):
...
/* The following constants should be used for the second parameter of
`shutdown'. */
enum
{
SHUT_RD = 0, /* No more receptions. */
#define SHUT_RD SHUT_RD
SHUT_WR, /* No more transmissions. */
#define SHUT_WR SHUT_WR
SHUT_RDWR /* No more receptions or transmissions. */
#define SHUT_RDWR SHUT_RDWR
};
...
my previous requests to the Berkeley DB developers to make db more
"versioning-friendly" were met with an unbelievable reply that I am
supposed to bundle a specific version of db with my program.

see berkeley-db/Makefile which should point you to modprep
http://clisp.cons.org/impnotes/modules.html#modprep

Well that's obvious :-)
What I would like to know, however, is: How is bdb.m.c generated, and
where do these symbols come from, if they are nowhere found in the source
code?

4.5 is not supported (yet).
see http://clisp.cons.org/impnotes/berkeley-db.html for the list of
supported versions.