testsuite/gdb.base/errno.exp

# Copyright 2024 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.

# Check that errno can be accessed by GDB under a variety of
# circumstances.
#
# The challenge with GDB accessing errno is that, on modern systems,
# errno is a variable in thread-local storage.  So, if GDB's access to
# thread local storage is broken or unavailable, some of these tests
# could fail.  On Linux, this is/was known to happen on systems with
# older versions of glibc as well as when debugging statically linked
# binaries.
#
# Another possibility is that the environment lacks sufficient
# type information to print errno.  This can happen for the errno
# variable itself or when the debuginfo contains a macro for errno
# which refers to a function lacking type information.
#
# When debugging core files, access to errno might not be possible
# both due to the situations described earlier along with the fact
# that inferior function calls are not possible (for the cases in
# which errno is a macro which calls a function returning errno's
# address).
#
# It's also possible for a program to declare errno in an inner scope
# causing the thread-local errno to be shadowed.  GDB should still
# correctly print the masking errno for this case.
#
# At the time that this test was written, on GNU/Linux and on FreeBSD,
# there were always scenarios in which printing errno was problematic.
# This test attempts to identify the problem cases and set up xfails
# for them.  So, hopefully, there should be no actual failures.  But
# the "expected" failures encountered by running this test do
# genuinely illustrate problems that a user might encounter while
# attempting to print errno.

standard_testfile

proc do_tests {{do_xfail_cast 0} {do_xfail 0} {do_xfail_core_test 0}} {
    clean_restart $::binfile
    if ![runto_main] {
	return
    }

    gdb_breakpoint [gdb_get_line_number "main-breakpoint"]
    gdb_continue_to_breakpoint "main-breakpoint"

    # Whether or not "print errno" will work often depends on the
    # debuginfo available.  We can make some inferences about whether
    # some of the tests should have xfail set-up by looking at the
    # output of "ptype errno".  This test is set up to always pass
    # even for less than ideal outputs, because the point is to set up
    # the xfail(s).
    gdb_test_multiple "ptype errno" "check errno type availability" {
	-re -wrap "type = int" {
	    pass $gdb_test_name
	}
	-re -wrap "type = .*no debug info.*" {
	    pass $gdb_test_name
	    set do_xfail 1
	    set do_xfail_core_test 1
	}
	-re -wrap "Cannot find thread-local variables on this target.*" {
	    pass $gdb_test_name
	    set do_xfail 1
	    set do_xfail_core_test 1
	    set do_xfail_cast 1
	}
	-re -wrap "Cannot find thread-local storage.*" {
	    pass $gdb_test_name
	    set do_xfail 1
	    set do_xfail_core_test 1
	    set do_xfail_cast 1
	}
	-re -wrap "has unknown return type; cast the call to its declared return type.*" {

	    # On systems which glibc as the C library, using -g3,
	    # which causes macro information to be included in the
	    # debuginfo, errno might be defined as follows:
	    #
	    #   #define errno (*__errno_location ())
	    #
	    # So, when we do "ptype errno", due to macro expansion,
	    # this ends up being "ptype (*__errno_location ())".  So
	    # the call to __errno_location (or something similar on
	    # other OSes) is the call mentioned in the error message.

	    pass $gdb_test_name
	    set do_xfail 1
	    set do_xfail_core_test 1
	    set do_xfail_cast 1
	}
    }

    # If errno is defined as a macro that contains an obvious function
    # call, it won't work when debugging a core file.
    gdb_test_multiple "info macro errno" "check if errno is a macro" {
	-re -wrap "Defined at.*\[\r\n\]#define.*\\\(\\\).*" {
	    set do_xfail_core_test 1
	    pass $gdb_test_name
	}
	-re -wrap "Defined at.*\[\r\n\]#define.*" {
	    pass $gdb_test_name
	}
	-re -wrap "The symbol .errno. has no definition.*" {
	    pass $gdb_test_name
	}
    }

    # Sometimes, "ptype errno" will ferret out that thread local
    # variables aren't accessible, but sometimes it won't.  Dig deeper
    # by trying to access memory using the "x/d" command.  Again, the
    # point here is to set up an xfail for the later tests, so we pass
    # this test for other known outputs.
    gdb_test_multiple "x/d &errno" "attempt to access errno memory" {
	-re -wrap "Cannot find thread-local variables on this target.*" {
	    pass $gdb_test_name
	    set do_xfail 1
	    set do_xfail_core_test 1
	    set do_xfail_cast 1
	}
	-re -wrap "Cannot find thread-local storage.*" {
	    pass $gdb_test_name
	    set do_xfail 1
	    set do_xfail_core_test 1
	    set do_xfail_cast 1
	}
	-re -wrap "has unknown return type; cast the call to its declared return type.*" {
	    set do_xfail 1
	    set do_xfail_core_test 1
	    set do_xfail_cast 1
	    pass $gdb_test_name
	}
	-re -wrap "$::hex.*?:\[\t \]$::decimal" {
	    pass $gdb_test_name
	}
    }

    if $do_xfail {
	setup_xfail *-*-*
    }
    gdb_test "print errno" ".* = 42"

    if $do_xfail_cast {
	setup_xfail *-*-*
    }
    gdb_test "print (int) errno" ".* = 42"

    set corefile ${::binfile}.core
    set core_supported 0
    if { ![is_remote host] } {
	set core_supported [gdb_gcore_cmd $corefile "save corefile"]
    }
    # Normally, we'd check core_supported here and return if it's
    # not, but we'll defer that until after the shadow test.

    gdb_breakpoint [gdb_get_line_number "shadow_errno-breakpoint"]
    gdb_continue_to_breakpoint "shadow_errno-breakpoint"

    # This test demonstrates why a simple hack to GDB for printing
    # errno is a bad idea.  (The hack was to intercept the string
    # "errno" in process_print_command_args() and replace it with
    # "*(*(int *(*)(void)) __errno_location) ()".)
    gdb_test "print errno" ".* = 36" "print masking errno"

    # Finish test early if no core file was made.
    if !$core_supported {
	return
    }

    clean_restart $::binfile

    set core_loaded [gdb_core_cmd $corefile "load corefile"]
    if { $core_loaded == -1 } {
	return
    }
    if $do_xfail_core_test {
	setup_xfail *-*-*
    }
    gdb_test "print errno" ".* = 42" "check errno value from corefile"
}

set binprefix $binfile

with_test_prefix "default" {
    set binfile $binprefix-default
    if  { [gdb_compile "${srcdir}/${subdir}/${srcfile}" "${binfile}" executable {debug}] != "" } {
	untested "failed to compile"
    } else {
	do_tests
    }
}

with_test_prefix "macros" {
    set binfile $binprefix-macros
    if  { [gdb_compile "${srcdir}/${subdir}/${srcfile}" "${binfile}" executable {debug macros}] != "" } {
	untested "failed to compile"
    } else {
	do_tests
    }
}

with_test_prefix "static" {
    set binfile $binprefix-static
    if  { [gdb_compile "${srcdir}/${subdir}/${srcfile}" "${binfile}" executable {debug "additional_flags=-static"}] != "" } {
	untested "failed to compile"
    } else {
	do_tests
    }
}

with_test_prefix "static-macros" {
    set binfile $binprefix-static-macros
    if  { [gdb_compile "${srcdir}/${subdir}/${srcfile}" "${binfile}" executable {debug macros "additional_flags=-static"}] != "" } {
	untested "failed to compile"
    } else {
	do_tests
    }
}

with_test_prefix "pthreads" {
    set binfile $binprefix-pthreads
    if  { [gdb_compile_pthreads "${srcdir}/${subdir}/${srcfile}" "${binfile}" executable {debug}] != "" } {
	untested "failed to compile"
    } else {
	do_tests
    }
}

with_test_prefix "pthreads-macros" {
    set binfile $binprefix-pthreads-macros
    if  { [gdb_compile_pthreads "${srcdir}/${subdir}/${srcfile}" "${binfile}" executable {debug macros}] != "" } {
	untested "failed to compile"
    } else {
	do_tests
    }
}

with_test_prefix "pthreads-static" {
    set binfile $binprefix-pthreads-static
    if  { [gdb_compile_pthreads "${srcdir}/${subdir}/${srcfile}" "${binfile}" executable {debug "additional_flags=-static"}] != "" } {
	untested "failed to compile"
    } else {
	do_tests
    }
}

with_test_prefix "pthreads-static-macros" {
    set binfile $binprefix-pthreads-static-macros
    if  { [gdb_compile_pthreads "${srcdir}/${subdir}/${srcfile}" "${binfile}" executable {debug macros "additional_flags=-static"}] != "" } {
	untested "failed to compile"
    } else {
	do_tests
    }
}