binutils-gdb/gdb/testsuite/lib/future.exp
Sergio Durigan Junior 57e5e64501 Implement dump of mappings with ELF headers by gcore
This patch has a long story, but it all started back in 2015, with
commit df8411da08 ("Implement support
for checking /proc/PID/coredump_filter").  The purpose of that commit
was to bring GDB's corefile generation closer to what the Linux kernel
does.  However, back then, I did not implement the full support for
the dumping of memory mappings containing ELF headers (like mappings
of DSOs or executables).  These mappings were being dumped most of
time, though, because the default value of /proc/PID/coredump_filter
is 0x33, which would cause anonymous private mappings (DSOs/executable
code mappings have this type) to be dumped.  Well, until something
happened on binutils...

A while ago, I noticed something strange was happening with one of our
local testcases on Fedora GDB: it was failing due to some strange
build-id problem.  On Fedora GDB, we (unfortunately) carry a bunch of
"local" patches, and some of these patches actually extend upstream's
build-id support in order to generate more useful information for the
user of a Fedora system (for example, when the user loads a corefile
into GDB, we detect whether the executable that generated that
corefile is present, and if it's not we issue a warning suggesting
that it should be installed, while also providing the build-id of the
executable).  A while ago, Fedora GDB stopped printing those warnings.

I wanted to investigate this right away, and spent some time trying to
determine what was going on, but other things happened and I got
sidetracked.  Meanwhile, the bug started to be noticed by some of our
users, and its priority started changing.  Then, someone on IRC also
mentioned the problem, and when I tried helping him, I noticed he
wasn't running Fedora.  Hm...  So maybe the bug was *also* present
upstream.

After "some" time investigating, and with a lot of help from Keith and
others, I was finally able to determine that yes, the bug is also
present upstream, and that even though it started with a change in ld,
it is indeed a GDB issue.

So, as I said, the problem started with binutils, more specifically
after the following commit was pushed:

  commit f6aec96dce
  Author: H.J. Lu <hjl.tools@gmail.com>
  Date:   Tue Feb 27 11:34:20 2018 -0800

      ld: Add --enable-separate-code

This commit makes ld use "-z separate-code" by default on x86-64
machines.  What this means is that code pages and data pages are now
separated in the binary, which is confusing GDB when it tries to decide
what to dump.

BTW, Fedora 28 binutils doesn't have this code, which means that
Fedora 28 GDB doesn't have the problem.  From Fedora 29 on, binutils
was rebased and incorporated the commit above, which started causing
Fedora GDB to fail.

Anyway, the first thing I tried was to pass "-z max-page-size" and
specify a bigger page size (I saw a patch that did this and was
proposed to Linux, so I thought it might help).  Obviously, this
didn't work, because the real "problem" is that ld will always use
separate pages for code and data.  So I decided to look into how GDB
dumped the pages, and that's where I found the real issue.

What happens is that, because of "-z separate-code", the first two pages
of the ELF binary are (from /proc/PID/smaps):

  00400000-00401000 r--p 00000000 fc:01 799548                             /file
  Size:                  4 kB
  KernelPageSize:        4 kB
  MMUPageSize:           4 kB
  Rss:                   4 kB
  Pss:                   4 kB
  Shared_Clean:          0 kB
  Shared_Dirty:          0 kB
  Private_Clean:         4 kB
  Private_Dirty:         0 kB
  Referenced:            4 kB
  Anonymous:             0 kB
  LazyFree:              0 kB
  AnonHugePages:         0 kB
  ShmemPmdMapped:        0 kB
  Shared_Hugetlb:        0 kB
  Private_Hugetlb:       0 kB
  Swap:                  0 kB
  SwapPss:               0 kB
  Locked:                0 kB
  THPeligible:    0
  VmFlags: rd mr mw me dw sd
  00401000-00402000 r-xp 00001000 fc:01 799548                             /file
  Size:                  4 kB
  KernelPageSize:        4 kB
  MMUPageSize:           4 kB
  Rss:                   4 kB
  Pss:                   4 kB
  Shared_Clean:          0 kB
  Shared_Dirty:          0 kB
  Private_Clean:         0 kB
  Private_Dirty:         4 kB
  Referenced:            4 kB
  Anonymous:             4 kB
  LazyFree:              0 kB
  AnonHugePages:         0 kB
  ShmemPmdMapped:        0 kB
  Shared_Hugetlb:        0 kB
  Private_Hugetlb:       0 kB
  Swap:                  0 kB
  SwapPss:               0 kB
  Locked:                0 kB
  THPeligible:    0
  VmFlags: rd ex mr mw me dw sd

Whereas before, we had only one:

  00400000-00401000 r-xp 00000000 fc:01 798593                             /file
  Size:                  4 kB
  KernelPageSize:        4 kB
  MMUPageSize:           4 kB
  Rss:                   4 kB
  Pss:                   4 kB
  Shared_Clean:          0 kB
  Shared_Dirty:          0 kB
  Private_Clean:         0 kB
  Private_Dirty:         4 kB
  Referenced:            4 kB
  Anonymous:             4 kB
  LazyFree:              0 kB
  AnonHugePages:         0 kB
  ShmemPmdMapped:        0 kB
  Shared_Hugetlb:        0 kB
  Private_Hugetlb:       0 kB
  Swap:                  0 kB
  SwapPss:               0 kB
  Locked:                0 kB
  THPeligible:    0
  VmFlags: rd ex mr mw me dw sd

Notice how we have "Anonymous" data mapped into the page.  This will be
important.

So, the way GDB decides which pages it should dump has been revamped
by my patch in 2015, and now it takes the contents of
/proc/PID/coredump_filter into account.  The default value for Linux
is 0x33, which means:

  Dump anonymous private, anonymous shared, ELF headers and HugeTLB
  private pages.

Or:

  filter_flags filterflags = (COREFILTER_ANON_PRIVATE
			      | COREFILTER_ANON_SHARED
			      | COREFILTER_ELF_HEADERS
			      | COREFILTER_HUGETLB_PRIVATE);

Now, it is important to keep in mind that GDB doesn't always have *all*
of the necessary information to exactly determine the type of a page, so
the whole algorithm is based on heuristics (you can take a look at
linux-tdep.c:dump_mapping_p and
linux-tdep.c:linux_find_memory_regions_full for more info).

Before the patch to make ld use "-z separate-code", the (single) page
containing data and code was being flagged as an anonymous (due to the
non-zero "Anonymous:" field) private (due to the "r-xp" permission),
which means that it was being dumped into the corefile.  That's why it
was working fine.

Now, as you can imagine, when "-z separate-code" is used, the *data*
page (which is where the ELF notes are, including the build-id one) now
doesn't have any "Anonymous:" mapping, so the heuristic is flagging it
as file-backed private, which is *not* dumped by default.

The next question I had to answer was: how come a corefile generated by
the Linux kernel was correct?  Well, the answer is that GDB, unlike
Linux, doesn't actually implement the COREFILTER_ELF_HEADERS support.
On Linux, even though the data page is also treated as a file-backed
private mapping, it is also checked to see if there are any ELF headers
in the page, and then, because we *do* have ELF headers there, it is
dumped.

So, after more time trying to think of ways to fix this, I was able to
implement an algorithm that reads the first few bytes of the memory
mapping being processed, and checks to see if the ELF magic code is
present.  This is basically what Linux does as well, except that, if
it finds the ELF magic code, it just dumps one page to the corefile,
whereas GDB will dump the whole mapping.  But I don't think that's a
big issue, to be honest.

It's also important to explain that we *only* perform the ELF magic
code check if:

  - The algorithm has decided *not* to dump the mapping so far, and;
  - The mapping is private, and;
  - The mapping's offset is zero, and;
  - The user has requested us to dump mappings with ELF headers.

IOW, we're not going to blindly check every mapping.

As for the testcase, I struggled even more trying to write it.  Since
our build-id support on upstream GDB is not very extensive, it's not
really possible to determine whether a corefile contains build-id
information or not just by using GDB.  So, after thinking a lot about
the problem, I decided to rely on an external tool, eu-unstrip, in
order to verify whether the dump was successful.  I verified the test
here on my machine, and everything seems to work as expected (i.e., it
fails without the patch, and works with the patch applied).  We are
working hard to upstream our "local" Fedora GDB patches, and we intend
to submit our build-id extension patches "soon", so hopefully we'll be
able to use GDB itself to perform this verification.

I built and regtested this on the BuildBot, and no problems were
found.

gdb/ChangeLog:
2019-04-25  Sergio Durigan Junior  <sergiodj@redhat.com>

	PR corefiles/11608
	PR corefiles/18187
	* linux-tdep.c (dump_mapping_p): Add new parameters ADDR and
	OFFSET.  Verify if current mapping contains an ELF header.
	(linux_find_memory_regions_full): Adjust call to
	dump_mapping_p.

gdb/testsuite/ChangeLog:
2019-04-25  Sergio Durigan Junior  <sergiodj@redhat.com>

	PR corefiles/11608
	PR corefiles/18187
	* gdb.base/coredump-filter-build-id.exp: New file.
2019-04-25 14:21:18 -04:00

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# Copyright 2004-2019 Free Software Foundation, Inc.
#
# This program is free software; you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation; either version 3 of the License, or
# (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program. If not, see <http://www.gnu.org/licenses/>.
load_lib libgloss.exp
# FIXME:brobecker/2004-03-31:
# The following functions should eventually be part of dejagnu. Even after
# these functions becomes available in dejagnu, we will keep for a while
# a copy here in order to avoid increasing the dejagnu version
# requirement.
proc gdb_find_gnatmake {} {
global tool_root_dir
set root "$tool_root_dir/gcc"
set GM ""
if ![is_remote host] {
set file [lookfor_file $root gnatmake]
if { $file != "" } {
set GM "$file -I$root/ada/rts --GCC=$root/xgcc --GNATBIND=$root/gnatbind --GNATLINK=$root/gnatlink -cargs -B$root -largs --GCC=$root/xgcc -margs";
}
}
if {$GM == ""} {
set GM [transform gnatmake]
}
return $GM
}
proc gdb_find_gdc {} {
global tool_root_dir
print "Tool Root: $tool_root_dir"
if {![is_remote host]} {
set file [lookfor_file $tool_root_dir gdc]
if { $file == "" } {
set file [lookfor_file $tool_root_dir gcc/gdc]
}
if { $file != "" } {
set CC "$file -B[file dirname $file]/"
} else {
set CC [transform gdc]
}
} else {
set CC [transform gdc]
}
print "CC: $CC"
return $CC
}
proc gdb_find_gfortran {} {
global tool_root_dir
if {![is_remote host]} {
set file [lookfor_file $tool_root_dir gfortran]
if { $file == "" } {
set file [lookfor_file $tool_root_dir gcc/gfortran]
}
if { $file != "" } {
set CC "$file -B[file dirname $file]/"
} else {
set CC [transform gfortran]
}
} else {
set CC [transform gfortran]
}
return $CC
}
proc gdb_find_go {} {
global tool_root_dir
set GO ""
if {![is_remote host]} {
set file [lookfor_file $tool_root_dir gccgo]
if { $file != "" } {
set root [file dirname $file]
set GO "$file -B$root/gcc/"
}
}
if { $GO == "" } {
set GO [transform gccgo]
}
return $GO
}
proc gdb_find_go_linker {} {
return [find_go]
}
proc gdb_find_rustc {} {
global tool_root_dir
if {![is_remote host]} {
set rustc [lookfor_file $tool_root_dir rustc]
if {$rustc == ""} {
set rustc rustc
}
} else {
set rustc ""
}
if {$rustc != ""} {
append rustc " --color never"
}
return $rustc
}
proc gdb_find_ldd {} {
global LDD_FOR_TARGET
if [info exists LDD_FOR_TARGET] {
set ldd $LDD_FOR_TARGET
} else {
set ldd "ldd"
}
return $ldd
}
proc gdb_find_objcopy {} {
global OBJCOPY_FOR_TARGET
if [info exists OBJCOPY_FOR_TARGET] {
set objcopy $OBJCOPY_FOR_TARGET
} else {
set objcopy [transform objcopy]
}
return $objcopy
}
# find target objdump
proc gdb_find_objdump {} {
global OBJDUMP_FOR_TARGET
if [info exists OBJDUMP_FOR_TARGET] {
set objdump $OBJDUMP_FOR_TARGET
} else {
set objdump [transform objdump]
}
return $objdump
}
proc gdb_find_readelf {} {
global READELF_FOR_TARGET
if [info exists READELF_FOR_TARGET] {
set readelf $READELF_FOR_TARGET
} else {
set readelf [transform readelf]
}
return $readelf
}
proc gdb_find_eu-unstrip {} {
global EU_UNSTRIP_FOR_TARGET
if [info exists EU_UNSTRIP_FOR_TARGET] {
set eu_unstrip $EU_UNSTRIP_FOR_TARGET
} else {
set eu_unstrip [transform eu-unstrip]
}
return $eu_unstrip
}
proc gdb_default_target_compile {source destfile type options} {
global target_triplet
global tool_root_dir
global CFLAGS_FOR_TARGET
global compiler_flags
if { $destfile == "" && $type != "preprocess" && $type != "none" } {
error "Must supply an output filename for the compile to default_target_compile"
}
set early_flags ""
set add_flags ""
set libs ""
set compiler_type "c"
set compiler ""
set linker ""
# linker_opts_order is one of "sources-then-flags", "flags-then-sources".
# The order matters for things like -Wl,--as-needed. The default is to
# preserve existing behavior.
set linker_opts_order "sources-then-flags"
set ldflags ""
set dest [target_info name]
if {[info exists CFLAGS_FOR_TARGET]} {
append add_flags " $CFLAGS_FOR_TARGET"
}
if {[info exists target_info(host,name)]} {
set host [host_info name]
} else {
set host "unix"
}
foreach i $options {
if { $i == "ada" } {
set compiler_type "ada"
if {[board_info $dest exists adaflags]} {
append add_flags " [target_info adaflags]"
}
if {[board_info $dest exists gnatmake]} {
set compiler [target_info gnatmake]
} else {
set compiler [find_gnatmake]
}
}
if { $i == "c++" } {
set compiler_type "c++"
if {[board_info $dest exists cxxflags]} {
append add_flags " [target_info cxxflags]"
}
append add_flags " [g++_include_flags]"
if {[board_info $dest exists c++compiler]} {
set compiler [target_info c++compiler]
} else {
set compiler [find_g++]
}
}
if { $i == "d" } {
set compiler_type "d"
if {[board_info $dest exists dflags]} {
append add_flags " [target_info dflags]"
}
if {[board_info $dest exists dcompiler]} {
set compiler [target_info dcompiler]
} else {
set compiler [find_gdc]
}
}
if { $i == "f77" } {
set compiler_type "f77"
if {[board_info $dest exists f77flags]} {
append add_flags " [target_info f77flags]"
}
if {[board_info $dest exists f77compiler]} {
set compiler [target_info f77compiler]
} else {
set compiler [find_g77]
}
}
if { $i == "f90" } {
set compiler_type "f90"
if {[board_info $dest exists f90flags]} {
append add_flags " [target_info f90flags]"
}
if {[board_info $dest exists f90compiler]} {
set compiler [target_info f90compiler]
} else {
set compiler [find_gfortran]
}
}
if { $i == "go" } {
set compiler_type "go"
if {[board_info $dest exists goflags]} {
append add_flags " [target_info goflags]"
}
if {[board_info $dest exists gocompiler]} {
set compiler [target_info gocompiler]
} else {
set compiler [find_go]
}
if {[board_info $dest exists golinker]} {
set linker [target_info golinker]
} else {
set linker [find_go_linker]
}
if {[board_info $dest exists golinker_opts_order]} {
set linker_opts_order [target_info golinker_opts_order]
}
}
if { $i == "rust" } {
set compiler_type "rust"
if {[board_info $dest exists rustflags]} {
append add_flags " [target_info rustflags]"
}
if {[board_info $dest exists rustflags]} {
set compiler [target_info rustflags]
} else {
set compiler [find_rustc]
}
}
if {[regexp "^dest=" $i]} {
regsub "^dest=" $i "" tmp
if {[board_info $tmp exists name]} {
set dest [board_info $tmp name]
} else {
set dest $tmp
}
}
if {[regexp "^compiler=" $i]} {
regsub "^compiler=" $i "" tmp
set compiler $tmp
}
if {[regexp "^early_flags=" $i]} {
regsub "^early_flags=" $i "" tmp
append early_flags " $tmp"
}
if {[regexp "^additional_flags=" $i]} {
regsub "^additional_flags=" $i "" tmp
append add_flags " $tmp"
}
if {[regexp "^ldflags=" $i]} {
regsub "^ldflags=" $i "" tmp
append ldflags " $tmp"
}
if {[regexp "^libs=" $i]} {
regsub "^libs=" $i "" tmp
append libs " $tmp"
}
if {[regexp "^incdir=" $i]} {
regsub "^incdir=" $i "-I" tmp
append add_flags " $tmp"
}
if {[regexp "^libdir=" $i]} {
regsub "^libdir=" $i "-L" tmp
append add_flags " $tmp"
}
if {[regexp "^ldscript=" $i]} {
regsub "^ldscript=" $i "" ldscript
}
if {[regexp "^redirect=" $i]} {
regsub "^redirect=" $i "" redirect
}
if {[regexp "^optimize=" $i]} {
regsub "^optimize=" $i "" optimize
}
if {[regexp "^timeout=" $i]} {
regsub "^timeout=" $i "" timeout
}
}
if {[board_info $host exists cflags_for_target]} {
append add_flags " [board_info $host cflags_for_target]"
}
global CC_FOR_TARGET
global CXX_FOR_TARGET
global D_FOR_TARGET
global F77_FOR_TARGET
global F90_FOR_TARGET
global GNATMAKE_FOR_TARGET
global GO_FOR_TARGET
global GO_LD_FOR_TARGET
global RUSTC_FOR_TARGET
if {[info exists GNATMAKE_FOR_TARGET]} {
if { $compiler_type == "ada" } {
set compiler $GNATMAKE_FOR_TARGET
}
}
if {[info exists CC_FOR_TARGET]} {
if { $compiler == "" } {
set compiler $CC_FOR_TARGET
}
}
if {[info exists CXX_FOR_TARGET]} {
if { $compiler_type == "c++" } {
set compiler $CXX_FOR_TARGET
}
}
if {[info exists D_FOR_TARGET]} {
if { $compiler_type == "d" } {
set compiler $D_FOR_TARGET
}
}
if {[info exists F77_FOR_TARGET]} {
if { $compiler_type == "f77" } {
set compiler $F77_FOR_TARGET
}
}
if {[info exists F90_FOR_TARGET]} {
if { $compiler_type == "f90" } {
set compiler $F90_FOR_TARGET
}
}
if { $compiler_type == "go" } {
if {[info exists GO_FOR_TARGET]} {
set compiler $GO_FOR_TARGET
}
if {[info exists GO_LD_FOR_TARGET]} {
set linker $GO_LD_FOR_TARGET
}
}
if {[info exists RUSTC_FOR_TARGET]} {
if {$compiler_type == "rust"} {
set compiler $RUSTC_FOR_TARGET
}
}
if { $type == "executable" && $linker != "" } {
set compiler $linker
}
if { $compiler == "" } {
set compiler [board_info $dest compiler]
if { $compiler == "" } {
return "default_target_compile: No compiler to compile with"
}
}
if {![is_remote host]} {
if { [which $compiler] == 0 } {
return "default_target_compile: Can't find $compiler."
}
}
if {$type == "object"} {
if {$compiler_type == "rust"} {
append add_flags "--emit obj"
} else {
append add_flags " -c"
}
}
if { $type == "preprocess" } {
append add_flags " -E"
}
if { $type == "assembly" } {
append add_flags " -S"
}
if {[board_info $dest exists cflags]} {
append add_flags " [board_info $dest cflags]"
}
if { $type == "executable" } {
if {[board_info $dest exists ldflags]} {
append add_flags " [board_info $dest ldflags]"
}
if { $compiler_type == "c++" } {
append add_flags " [g++_link_flags]"
}
if {[isnative]} {
# This is a lose.
catch "glob -nocomplain $tool_root_dir/libstdc++/libstdc++.so* $tool_root_dir/libstdc++/libstdc++.sl" tmp
if { ${tmp} != "" } {
if {[regexp ".*solaris2.*" $target_triplet]} {
# Solaris 2
append add_flags " -R$tool_root_dir/libstdc++"
} elseif {[regexp ".*(osf|irix5|linux).*" $target_triplet]} {
# OSF/1 or IRIX 5
append add_flags " -Wl,-rpath,$tool_root_dir/libstdc++"
}
}
}
}
if {![info exists ldscript]} {
set ldscript [board_info $dest ldscript]
}
foreach i $options {
if { $i == "debug" } {
if {[board_info $dest exists debug_flags]} {
append add_flags " [board_info $dest debug_flags]"
} else {
append add_flags " -g"
}
}
}
if {[info exists optimize]} {
append add_flags " $optimize"
}
if { $type == "executable" } {
append add_flags " $ldflags"
foreach x $libs {
if {[file exists $x]} {
append source " $x"
} else {
append add_flags " $x"
}
}
if {[board_info $dest exists libs]} {
append add_flags " [board_info $dest libs]"
}
# This probably isn't such a good idea, but it avoids nasty
# hackiness in the testsuites.
# The math library must be linked in before the C library. The C
# library is linked in by the linker script, so this must be before
# the linker script.
if {[board_info $dest exists mathlib]} {
append add_flags " [board_info $dest mathlib]"
} else {
append add_flags " -lm"
}
# This must be added here.
append add_flags " $ldscript"
if {[board_info $dest exists remote_link]} {
# Relink option.
append add_flags " -Wl,-r"
}
if {[board_info $dest exists output_format]} {
append add_flags " -Wl,-oformat,[board_info $dest output_format]"
}
}
if {[board_info $dest exists multilib_flags]} {
append add_flags " [board_info $dest multilib_flags]"
}
verbose "doing compile"
set sources ""
if {[is_remote host]} {
foreach x $source {
set file [remote_download host $x]
if { $file == "" } {
warning "Unable to download $x to host."
return "Unable to download $x to host."
} else {
append sources " $file"
}
}
} else {
set sources $source
}
if {[is_remote host]} {
append add_flags " -o " [file tail $destfile]
remote_file host delete [file tail $destfile]
} else {
if { $destfile != "" } {
append add_flags " -o $destfile"
}
}
# This is obscure: we put SOURCES at the end when building an
# object, because otherwise, in some situations, libtool will
# become confused about the name of the actual source file.
switch $type {
"object" {
set opts "$early_flags $add_flags $sources"
}
"executable" {
switch $linker_opts_order {
"flags-then-sources" {
set opts "$early_flags $add_flags $sources"
}
"sources-then-flags" {
set opts "$early_flags $sources $add_flags"
}
default {
error "Invalid value for board_info linker_opts_order"
}
}
}
default {
set opts "$early_flags $sources $add_flags"
}
}
if {[is_remote host]} {
if {[host_info exists use_at]} {
set fid [open "atfile" "w"]
puts $fid "$opts"
close $fid
set opts "@[remote_download host atfile]"
remote_file build delete atfile
}
}
verbose "Invoking the compiler as $compiler $opts" 2
if {[info exists redirect]} {
verbose "Redirecting output to $redirect" 2
set status [remote_exec host "$compiler $opts" "" "" $redirect]
} else {
if {[info exists timeout]} {
verbose "Setting timeout to $timeout" 2
set status [remote_exec host "$compiler $opts" "" "" "" $timeout]
} else {
set status [remote_exec host "$compiler $opts"]
}
}
set compiler_flags $opts
if {[is_remote host]} {
remote_upload host [file tail $destfile] $destfile
remote_file host delete [file tail $destfile]
}
set comp_output [prune_warnings [lindex $status 1]]
regsub "^\[\r\n\]+" $comp_output "" comp_output
if { [lindex $status 0] != 0 } {
verbose -log "compiler exited with status [lindex $status 0]"
}
if { [lindex $status 1] != "" } {
verbose -log "output is:\n[lindex $status 1]" 2
}
if { [lindex $status 0] != 0 && "${comp_output}" == "" } {
set comp_output "exit status is [lindex $status 0]"
}
return ${comp_output}
}
# See if the version of dejaGNU being used to run the testsuite is
# recent enough to contain support for building Ada programs or not.
# If not, then use the functions above in place of the ones provided
# by dejaGNU. This is only temporary (brobecker/2004-03-31).
set use_gdb_compile 0
if {[info procs find_gnatmake] == ""} {
rename gdb_find_gnatmake find_gnatmake
set use_gdb_compile 1
}
if {[info procs find_gfortran] == ""} {
rename gdb_find_gfortran find_gfortran
set use_gdb_compile 1
}
if {[info procs find_go_linker] == ""} {
rename gdb_find_go find_go
rename gdb_find_go_linker find_go_linker
set use_gdb_compile 1
}
if {[info procs find_gdc] == ""} {
rename gdb_find_gdc find_gdc
set use_gdb_compile 1
}
if {[info procs find_rustc] == ""} {
rename gdb_find_rustc find_rustc
set use_gdb_compile 1
}
if {$use_gdb_compile} {
catch {rename default_target_compile {}}
rename gdb_default_target_compile default_target_compile
}
# Provide 'lreverse' missing in Tcl before 7.5.
if {[info procs lreverse] == ""} {
proc lreverse { arg } {
set retval {}
while { [llength $retval] < [llength $arg] } {
lappend retval [lindex $arg end-[llength $retval]]
}
return $retval
}
}
# Various ccache versions provide incorrect debug info such as ignoring
# different current directory, breaking GDB testsuite.
set env(CCACHE_DISABLE) 1
unset -nocomplain env(CCACHE_NODISABLE)