More on FreeBSD/amd64

Hi Ian, I have made some more progress on understanding the build failure on FreeBSD/amd64. I could use a check on my understanding of the problem, though. The setup: I have an unregisterized ghc-6.4.2 successfully built on FreeBSD/amd64. It was bootstrapped from .hc files compiled on FreeBSD/i386. I am attempting to use this compiler (the ghc-inplace from the unregisterized build, not a fully installed compiler) to build a recent ghc-6.6 branch from darcs (20070314). The build of ghc-6.6-20070314 fails when compiling rts/Linker.c. The failure is mostly reproducible (more about that below). It's also worth remembering that when I tried to build an unregisterized ghc-6.6 on FreeBSD/amd64 using .hc files from ghc-6.6 built on FreeBSD/i386, I had a crash at the same place, while trying to build rts/Linker.c The failure comes from trying to allocate a huge amount of memory. newPinnedByteArrayzh_fast is called with a giant argument, 0x4000000010. So it looks like we're after 16 bytes, but the upper 32 bits has some junk in it. The above was the state of things just over a week ago. Since then, I've worked to track down whether the bug is in the ghc-6.4.2 runtime or in the ghc-6.6 code. The compiler that fails is the 6.6 stage1 compiler, which is a 6.6 compiler linked with the runtime from the unregisterized 6.4.2 (let me know if I'm wrong about that). I have rebuilt the unregisterized 6.4.2 with optimization turned off. I haven't got any more information this way; it seems the problem is really on the 6.6 side. Here is my reasoning: I run the 6.6 compiler under the debugger: greenhouse-george> gdb /tmp/ghc/compiler/stage1/ghc-6.6.20070314 GNU gdb 6.1.1 [FreeBSD] Copyright 2004 Free Software Foundation, Inc. GDB is free software, covered by the GNU General Public License, and you are welcome to change it and/or distribute copies of it under certain conditions. Type "show copying" to see the conditions. There is absolutely no warranty for GDB. Type "show warranty" for details. This GDB was configured as "amd64-marcel-freebsd"... (gdb) dir /tmp/ghc-6.4.2/ghc/rts Source directories searched: /tmp/ghc-6.4.2/ghc/rts:$cdir:$cwd (gdb) b newPinnedByteArrayzh_fast Breakpoint 1 at 0x163cbb4 (gdb) run -B/tmp/ghc -v -optc-O -optc-Wall -optc-W -optc-Wstrict- prototypes -optc-Wmissing-prototypes -optc-Wmissing-declarations - optc-Winline -optc-Waggregate-return -optc-Wbad-function-cast -optc- I../includes -optc-I. -optc-Iparallel -optc-DCOMPILING_RTS -optc- fomit-frame-pointer -optc-I/usr/local/include -optc-fno-strict- aliasing -H16m -O -optc-O2 -static -I/usr/local/include -I. -#include HCIncludes.h -fvia-C -dcmm-lint -c Linker.c -o Linker.o Starting program: /tmp/ghc/compiler/stage1/ghc-6.6.20070314 -B/tmp/ ghc -v -optc-O -optc-Wall -optc-W -optc-Wstrict-prototypes -optc- Wmissing-prototypes -optc-Wmissing-declarations -optc-Winline -optc- Waggregate-return -optc-Wbad-function-cast -optc-I../includes -optc- I. -optc-Iparallel -optc-DCOMPILING_RTS -optc-fomit-frame-pointer - optc-I/usr/local/include -optc-fno-strict-aliasing -H16m -O -optc-O2 - static -I/usr/local/include -I. -#include HCIncludes.h -fvia-C -dcmm- lint -c Linker.c -o Linker.o Breakpoint 1, 0x000000000163cbb4 in newPinnedByteArrayzh_fast () By playing around with it, I have isolated --- more or less --- when the failure occurs. In this run, it was after 973 calls to newPinnedByteArrayzh_fast. If I quit gdb and re-run it, the number of calls is consistently the same. However, from one system boot to the next, it varies a bit. Yesterday morning, I had to skip 976 calls. (gdb) c 973 Will ignore next 972 crossings of breakpoint 1. Continuing. Glasgow Haskell Compiler, Version 6.6.20070314, for Haskell 98, compiled by GHC version 6.4.2 Using package config file: /tmp/ghc/driver/package.conf.inplace wired-in package base not found. wired-in package rts mapped to rts-1.0 wired-in package haskell98 not found. wired-in package template-haskell not found. Hsc static flags: -static -static Created temporary directory: /tmp/ghc1073_0 *** C Compiler: gcc -x c Linker.c -o /tmp/ghc1073_0/ghc1073_0.s -v -S -Wimplicit -O - D__GLASGOW_HASKELL__=606 -O -Wall -W -Wstrict-prototypes -Wmissing- prototypes -Wmissing-declarations -Winline -Waggregate-return -Wbad- function-cast -I../includes -I. -Iparallel -DCOMPILING_RTS -fomit- frame-pointer -I/usr/local/include -fno-strict-aliasing -O2 -I /usr/ local/include -I . -I /tmp/ghc/includes -fwrapv Breakpoint 1, 0x000000000163cbb4 in newPinnedByteArrayzh_fast () OK, I should be at the call which is going to blow up: (gdb) bt #0 0x000000000163cbb4 in newPinnedByteArrayzh_fast () #1 0x00000000016377ea in StgRun (f=0x163cbb0 , basereg=0x260fcd0) at StgCRun.c:93 #2 0x0000000001631f48 in schedule (mainThread=0x2611080, initialCapability=0x0) at Schedule.c:932 #3 0x0000000001633190 in waitThread_ (m=0x2611080, initialCapability=0x0) at Schedule.c:2156 #4 0x0000000001633085 in scheduleWaitThread (tso=0x8021c0000, ret=0x0, initialCapability=0x0) at Schedule.c:2050 #5 0x000000000162d60f in rts_evalLazyIO (p=0x1d409d0, ret=0x0) at RtsAPI.c:459 #6 0x000000000162ca24 in main (argc=33, argv=0x7fffffffe960) at Main.c:104 (gdb) f 1 #1 0x00000000016377ea in StgRun (f=0x163cbb0 , basereg=0x260fcd0) at StgCRun.c:93 93 f = (StgFunPtr) (f)(); Since the 6.4.2 runtime is unregisterized, the parameter are passed through the virtual, not actual registers (is this correct?). The code for newPinnedByteArrayzh_fast says that the requested number of bytes is passed in through R1, so take a look: (gdb) p basereg->rR1 $1 = {w = 274877906960, a = 0x4000000010, c = 16, i8 = 16 '\020', f = 2.24207754e-44, i = 274877906960, p = 0x4000000010, cl = 0x4000000010, offset = 274877906960, b = 0x4000000010 , t = 0x4000000010} This request should certainly wedge the system by gobbling up all of the memory. The question now is what put the bad value into R1? It seems as if newPinnedByteArrayzh_fast is just getting too big a request. I looked at the assembly code for newPinnedByteArrayzh_fast, and the arguments passed down to the functions it calls are calculated correctly, but are just too big. I also tried setting the breakpoint one call earlier (972 instead of 973), and then stepping through until I reached the next breakpoint. newPinnedByteArrayzh_fast calls allocatePinned successfully and control come back to StgCRun.c at line 87. This is the miniinterpreter loop. If I keep stepping control just stays in the miniinterpreter loop until newPinnedByteArrayzh_fast is called again. (I used the gdb "until" command to run the loop until it either finished or hit a breakpoint. It hit the breakpoint.) This leads me to believe that the problem is in the haskell code, not the C code of the runtime system. Looking at the RTS stack, (gdb) pmem basereg->rSp 32 0x802dfe808: 0x0 0x802dfe800: 0x0 0x802dfe7f8: 0x2216f80 0x802dfe7f0: 0x2217000 0x802dfe7e8: 0x2149b90 0x802dfe7e0: 0x0 0x802dfe7d8: 0x2214b60 0x802dfe7d0: 0x2214b20 0x802dfe7c8: 0x802a121b0 0x802dfe7c0: 0x1d61f60 0x802dfe7b8: 0x802a15848 0x802dfe7b0: 0x1 0x802dfe7a8: 0x2214b60 0x802dfe7a0: 0x2214b40 0x802dfe798: 0x22179e0 0x802dfe790: 0x802a17af0 0x802dfe788: 0x802a17b08 0x802dfe780: 0x802a121b0 0x802dfe778: 0x802a15870 0x802dfe770: 0x1d61a40 0x802dfe768: 0x217aef0 0x802dfe760: 0x802a17b88 0x802dfe758: 0x802d04e98 0x802dfe750: 0x2125f40 0x802dfe748: 0x802a18970 0x802dfe740: 0x802a17b08 0x802dfe738: 0x802a17b78 0x802dfe730: 0x1d61620 0x802dfe728: 0x400000000 0x802dfe720: 0x802d04ed0 0x802dfe718: 0x400000000 0x802dfe710: 0x220db80 (gdb) I'm guessing that the culpable module defines the symbol "s31b". I added -ddump-stg to the options for the 6.6 build. (In fact, deleted everything, added the -ddump-stg option, rebuilt and did the run under the debugger shown above, to make certain that everything was consistent.) The symbol "s31b" is from the module GHC.Compat.Unicode. This may be getting somewhere. Compat.Unicode does not exist in 6.4.2, which may explain why the unregisterized 6.4.2 is quite reliable --- I used it to build alex and happy with no trouble. Also, the Unicode module makes foreign calls to C library functions. FreeBSD has its own implementation of libc, not the same as linux, which may explain why FreeBSD/amd64 chokes and Linux/amd64 works. So. I am asking if this argument makes sense, especially my interpretation of the RTS stack dump. Any suggestions are appreciated. Best Wishes, Greg