Opened 17 years ago

Closed 17 years ago

Last modified 3 weeks ago

#1 closed bug (Fixed)

Implicit parameters cause strange behavi

Reported by: nobody Owned by: nobody
Priority: normal Milestone:
Component: Compiler Version: 5.0
Keywords: Cc:
Operating System: Architecture:
Type of failure: None/Unknown Test Case:
Blocked By: Blocking:
Related Tickets: Differential Rev(s):
Wiki Page:


ghc-5.00.1 (with glasgow-exts) compiles the following

> foo :: ((?x :: Int) => b) -> Int -> b
> foo s z = s with ?x = z
> main = foo (print ?x) 42

Running the generated code prints nothing. (No output
is produced
even if we add putStr "Hello world\n" before the call
to foo).

Change History (6)

comment:1 Changed 17 years ago by simonpj

Status: assignedclosed
Logged In: YES 

Works fine with GHC 5.02 (about to be released)

comment:2 Changed 3 years ago by Sergei Trofimovich <siarheit@…>

In ade1a461/ghc:

Fix minimum alignment for StgClosure (Trac #11395)

The bug is observed on m68k-linux target as crash
in RTS:

    -- a.hs:
    main = print 43

    $ inplace/bin/ghc-stage1 --make -debug a.hs

    $ ./a
    Program terminated with signal SIGSEGV, Segmentation fault.
    #0  0x80463b0a in LOOKS_LIKE_INFO_PTR_NOT_NULL (p=32858)
        at includes/rts/storage/ClosureMacros.h:248
    (gdb) bt
    #0  0x80463b0a in LOOKS_LIKE_INFO_PTR_NOT_NULL (p=32858)
        at includes/rts/storage/ClosureMacros.h:248
    #1  0x80463b46 in LOOKS_LIKE_INFO_PTR (p=32858)
        at includes/rts/storage/ClosureMacros.h:253
    #2  0x80463b6c in LOOKS_LIKE_CLOSURE_PTR (
            p=0x805aac6e <stg_dummy_ret_closure>)
        at includes/rts/storage/ClosureMacros.h:258
    #3  0x80463e4c in initStorage ()
        at rts/sm/Storage.c:121
    #4  0x8043ffb4 in hs_init_ghc (...)
        at rts/RtsStartup.c:181
    #5  0x80455982 in hs_main (...)
        at rts/RtsMain.c:51
    #6  0x80003c1c in main ()

GHC assumes last 2 pointer bits are tags on 32-bit targets.
But here 'stg_dummy_ret_closure' address violates the assumption:

    LOOKS_LIKE_CLOSURE_PTR (p=0x805aac6e <stg_dummy_ret_closure>)

I've added compiler hint for static StgClosure objects to
align closures at least by their natural alignment (what GHC assumes).
See Note [StgWord alignment].

Signed-off-by: Sergei Trofimovich <>

Test Plan: ran basic test on m68k qemu, it got past ASSERTs

Reviewers: simonmar, austin, bgamari

Reviewed By: bgamari

Subscribers: thomie

Differential Revision:

GHC Trac Issues: #11395

comment:3 Changed 19 months ago by Ben Gamari <ben@…>

Type of failure: None/Unknown

In 5c95e6b7/ghc:

Remove outdated information about main() in HSrts (#1)

The main method is not contained in HSrts so the removed section is no longer valid.

comment:4 Changed 16 months ago by Ben Gamari <ben@…>

In 83ee930f/ghc:

fix a memory leak in osNumaMask

got an error when using asan:
==1866689==ERROR: LeakSanitizer: detected memory leaks

Direct leak of 16 byte(s) in 1 object(s) allocated from:
    #0 0x10640568 in malloc ??:?
    #1 0x154d867e in numa_bitmask_alloc .../numactl-2.0.8/libnuma_nosymve r.c:204
    #2 0x154d867e in numa_allocate_nodemask .../numactl-2.0.8/libnuma_nosymve r.c:724
    #3 0x154d867e in numa_get_mems_allowed .../numactl-2.0.8/libnuma_nosymve r.c:1141
    #4 0x10b54a45 in osNumaMask ...ghc-8.0.2/rts/posix/OSMem.c:59 8

Test Plan: compile, validate

Reviewers: simonmar, niteria, austin, bgamari, erikd

Reviewed By: bgamari

Subscribers: rwbarton, thomie

Differential Revision:

comment:5 Changed 15 months ago by Ben Gamari <ben@…>

In b8f33bc6/ghc:

Always allow -staticlib

the `-staticlib` flag is currently only supported on apple platforms,
due to the avaiablity of libtool (the apple version, which is unlike the
gnu version).  This however prevents the use of -staticlib in cases
where it would be beneficial as well.  The functionality that
`-staticlib` uses from `libtool` can be stubbed with a small script like
the following:


# This script pretends to be libtool.  And supports
# only a limited set of flags.
# It is supposed to be a stand in for libtool -static, whic
# creates a static archive.  This is done by locating all -l<lib>
# libs in the provied -L<lib path> library paths, and building an
# MRI script to create the final archive from all the libraries, and
# other provided inputs.


set -e


# find_lib <name> path path path path
function find_lib () {
        lib=$1; shift 1;
        for dir in $@; do
                if [ -f "$dir/$lib" ]; then
                        echo "$dir/$lib"

while [ "$#" -gt 0 ]; do
        case "$1" in
                -v|--verbose) verbose=1; shift 1;;
                -o) output="$2"; shift 2;;
                -L*) ldflags_L+=("${1:2:${#1}-2}"); shift 1;;
                -l*) ldflags_l+=("lib${1:2:${#1}-2}.a"); shift 1;;
                -static) mode=$STATIC; shift 1;;
                -dynamic) mode=$DYNAMIC; shift 1;;
                -Wl,*) ldflags+=("${1#*,}"); shift 1;;
                -*) echo "unknown option: $1" >&2; exit 1;;
                *) inputs+=("$1"); shift 1;;

if [ ! $mode == $STATIC ]; then
        echo "-dynamic not supported!" >&2; exit 1;

MRI="create ${output}\n"
for input in "${ldflags_l[@]}"; do
        lib=$(find_lib $input ${ldflags_L[@]})
        if [ -z $lib ]; then
                echo "Failed to find lib $input" >&2
                exit 1
                MRI+="addlib $lib\n"
for input in "${inputs[@]}"; do
        MRI+="addmod $input\n"
echo -e "$MRI" | $target-ar -M
$target-ranlib $output

if `ar` supports MRI scripts.

Reviewers: austin, bgamari

Reviewed By: bgamari

Subscribers: rwbarton, thomie

Differential Revision:

comment:6 Changed 3 months ago by Ben Gamari <ben@…>

In 91822e4e/ghc:

Add "quantified constraint" context in error message, fix #15231.

This patch adds "quantified constraint" context in error message when
UndecidableInstances checking fails for quantified constraints.
See Trac #15231:comment#1.

This patch also pretty-prints the instance head for better error messages.

Test Plan: make test TEST="T15231"

Reviewers: bgamari, simonpj

Reviewed By: simonpj

Subscribers: simonpj, rwbarton, thomie, carter

GHC Trac Issues: #15231

Differential Revision:
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