Bug reports should be sent to mercury-bugs@cs.mu.oz.au. If you're reporting more than one bug, please use separate emails for each bug. Please include all the relevant information, including which version of Mercury you're using, what operating system you're using, and a complete source file that demonstrates the problem. (If it's something that only shows up in multi-module programs, send a shar archive or uuencoded tar archive containing your source files.) Please try to ensure that bug reports contain all the information that we need to be able to reproduce the problem. Make sure that all bug reports are fully self-contained. Below is a list of the known outstanding bugs. We'll try to record any other bugs that are discovered on our WWW page . In addition to the bugs mentioned here, some bugs related to the implementation of particular languages features (existential types, nested modules, tabling) are also mentioned in the language reference manual, and some problems related to using Mercury on specific operating systems are described in the README.* files. See also the LIMITATIONS file. Note: please do not be alarmed by the fact that this software has some bugs. ALL useful software has bugs. During the development of the Mercury implementation we have found bugs in gcc, as, ld, the dynamic loader, and even the OS kernel. We hope that by listing the known outstanding bugs here we are doing our users a service. It would be disappointing if anyone were to infer the wrong thing from it. ----------------------------------------------------------------------------- Subject: GCC internal error Date: Tue, 26 June 2001 random.c: In function `random_module6': random.c:412: fixed or forbidden register 3 (bx) was spilled for class GENERAL_REGS. This may be due to a compiler bug or to impossible asm statements or clauses. mercury_trace_alias.c:98: Unable to find a register to spill in class `SIREG'. This problem occurs with several different combinations of GCC version and C source file. This seems to be a bug in GCC's handling of global register variables. The bug seems to be finally fixed in GCC 3.3 or 3.4. If this problem occurs when compiling the source distribution, install from the binary distribution instead. If a similar problem occurs when compiling your program, there are a few possible work-arounds: * Use a lower level of C compiler optimization for the affected C files (add `CFLAGS-foo = -O1' or `CFLAGS-foo = -O0' to your Mmakefile for each affected C file). * Use a high-level C code compilation grade (add `GRADE = hlc.gc' to your Mmakefile). These grades do not use the GCC extensions which trigger this problem. Unfortunately, mdb does not yet work with the high-level C back-end. * Use `asm_jump.*' compilation grades instead of `asm_fast.*' grades. Note that `asm_jump.*' grades are not usually installed. * Try a newer version of GCC. Avoid GCC version 2.96 (distributed by Red Hat) and 3.0. ----------------------------------------------------------------------------- Subject: bug report - Inf and NaN Date: Wed, 4 Oct 1995 02:48:19 +1000 (EST) The following module causes an "undefined variable Inf" error in the generated C code, because 1E400 == Infinity, which gets printed as `Inf'. :- module hello. :- interface. :- import_module io. :- pred main(io__state::di, io__state::uo) is det. :- implementation. main --> io__write_float(1E400), io__write_string("\n"). ----------------------------------------------------------------------------- Subject: NaN behaviour Date: Mon, 21 Oct 2002 21:02:00 +1000 The mercury standard library tends to avoid producing NaN (e.g. throwing an exception in many places where libc would return NaN), but it's still possible from arithmetic functions (e.g. 0.0*Inf, Inf - Inf, Inf + -Inf, Inf / Inf), sin,cos,tan when passed infinity, and perhaps other things (I haven't done a full search). Presumably it can also arise from using the foreign language interface. When NaN does arise, we have a problem that `=' (and unification) aren't reflexive. From a logical point of view, this is a fairly serious problem. A lesser problem is that `<' doesn't induce a total order on floats. ----------------------------------------------------------------------------- Subject: nit in error msg Date: Thu, 16 May 1996 10:25:42 +1000 (EST) Here's another small error in an error message. If you comment out the [] clause for the functions car/1 or cdr/1, you get this message: fntest.m:023: In `car(in) = out': fntest.m:023: Error: determinism declaration not satisfied. fntest.m:023: Declared `det', inferred `semidet'. fntest.m:023: in argument 1 of clause head: fntest.m:023: unification of `HeadVar__1' and `[X | V_4]' can fail. It says Declared `det', inferred `semidet', but I never declared it at all. It's a bit misleading. Certainly not a major problem, and the later part of the message makes it quite clear what the problem is, but I thought I'd point it out to you before I forgot it. ----------------------------------------------------------------------------- Subject: bug with PC values on Alpha Date: Wed, 12 Jun 1996 15:45:59 +1000 On the alpha, if the Mercury runtime catches a signal, it sometimes prints out the wrong value for the PC. ----------------------------------------------------------------------------- Subject: inter-module optimization and abstract exported equivalence types. Date: Thu, 19 February 1998 In some cases the compiler reports spurious ambiguity errors when compiling with `--intermodule-optimization'. This is due to the definition of abstract exported equivalence types being made visible by inter-module optimization. In this example, with `--intermodule-optimization' the compiler sees the declaration `:- type var == int' from term.m and then cannot determine whether `Elem' has type `int' or `pair(int)'. The work-around is to add an explicit type qualification. :- module foo. :- interface. :- import_module list, term. :- pred test(list(var)::in) is det. :- implementation. :- import_module int, std_util. test(Args0) :- MakeIndex = (pred(Elem0::in, Elem::out, Index0::in, Index::out) is det :- Elem = Elem0 - Index0, Index is Index0 + 1 ), list.map_foldl(MakeIndex, Args0, _, 0, _). ----------------------------------------------------------------------------- Subject: mode analysis bug Date: 1 December 2004 The Mercury compiler sometimes aborts with the following error message: Uncaught Mercury exception: Software Error: inappropriate determinism inside a negation This bug is due to a limitation in the mode checker. It has only been reported as occurring when inlining is enabled. A workaround is to disable inlining for any affected files. This can be done by using the option `--no-inlining'. -----------------------------------------------------------------------------