binutils-gdb/gdb/testsuite/gdb.gdb/index-file.exp

# Copyright 2023-2025 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 the GDB executable, and then 'save gdb-index', and make some
# checks of the generated index file.

load_lib selftest-support.exp

# Can't save an index with readnow.
require !readnow

# A multiplier used to ensure slow tasks are less likely to timeout.
set timeout_factor 20

set filename [selftest_prepare]
if { $filename eq "" } {
    unsupported "${gdb_test_file_name}.exp"
    return -1
}

# If FILENAME is a libtool wrapper, then we need to get the path of the real
# executable.
set filename [selftest_libtool_get_real_gdb_executable $filename]
if { $filename eq "" } {
    return -1
}

with_timeout_factor $timeout_factor {
    # Start GDB, load FILENAME.
    clean_restart
    gdb_load $filename
}

# Record how many worker threads GDB is using.
set worker_threads [gdb_get_worker_threads]

if { $worker_threads eq "UNKNOWN" } {
    unresolved "unable to get worker thread count"
    return -1
}

# Generate an index file.
set dir1 [standard_output_file "index_1"]
remote_exec host "mkdir -p ${dir1}"
with_timeout_factor $timeout_factor {
    set ok 0
    gdb_test_multiple "save gdb-index $dir1" "create gdb-index file" {
	-re -wrap "Error while writing index for \[^\r\n\]*: No debugging symbols" {
	    unsupported $gdb_test_name
	}
	-re -wrap "^" {
	    pass $gdb_test_name
	    set ok 1
	}
    }
    if { ! $ok } {
	return -1
    }

    gdb_test_no_output "save gdb-index -dwarf-5 $dir1" \
	"create dwarf-index files"
}

# Close GDB.
gdb_exit

# Validate that the index-file FILENAME has made efficient use of its
# symbol hash table.  Calculate the number of symbols in the hash
# table and the total hash table size.  The hash table starts with
# 1024 entries, and then doubles each time it is filled to 75%.  At
# 75% filled, doubling the size takes it to 37.5% filled.
#
# Thus, the hash table is correctly filled if:
#  1. Its size is 1024 (i.e. it has not yet had its first doubling), or
#  2. Its filled percentage is over 37%
#
# We could check that it is not over filled, but I don't as that's not
# really an issue.  But we did once have a bug where the table was
# doubled incorrectly, in which case we'd see a filled percentage of
# around 2% in some cases, which is a huge waste of disk space.
proc check_symbol_table_usage { filename } {
    # Open the file in binary mode and read-only mode.
    set fp [open $filename rb]

    # Configure the channel to use binary translation.
    fconfigure $fp -translation binary

    # Read the first 8 bytes of the file, which contain the header of
    # the index section.
    set header [read $fp [expr 7 * 4]]

    # Scan the header to get the version, the CU list offset, and the
    # types CU list offset.
    binary scan $header iiiiii version \
	_ _ _ symbol_table_offset shortcut_offset

    # The length of the symbol hash table (in entries).
    set len [expr {($shortcut_offset - $symbol_table_offset) / 8}]

    # Now walk the hash table and count how many entries are in use.
    set offset $symbol_table_offset
    set count 0
    while { $offset < $shortcut_offset } {
	seek $fp $offset
	set entry [read $fp 8]
	binary scan $entry ii name_ptr flags
	if { $name_ptr != 0 } {
	    incr count
	}

	incr offset 8
    }

    # Close the file.
    close $fp

    # Calculate how full the cache is.
    set pct [expr {(100 * double($count)) / $len}]

    # Write our results out to the gdb.log.
    verbose -log "Hash table size: $len"
    verbose -log "Hash table entries: $count"
    verbose -log "Percentage usage: $pct%"

    # The minimum fill percentage is actually 37.5%, but we give TCL a
    # little flexibility in case the FP maths give a result a little
    # off.
    gdb_assert { $len == 1024 || $pct > 37 } \
	"symbol hash table usage"
}

set index_filename_base [file tail $filename]
check_symbol_table_usage "$dir1/${index_filename_base}.gdb-index"

# If GDB is using more than 1 worker thread then reduce the number of
# worker threads, regenerate the index, and check that we get the same
# index file back.  At one point the layout of the index would vary
# based on the number of worker threads used.
if { $worker_threads > 1 } {
    # Start GDB, but don't load a file yet.
    clean_restart

    # Adjust the number of threads to use.
    set reduced_threads [expr {$worker_threads / 2}]
    gdb_test_no_output "maint set worker-threads $reduced_threads"

    with_timeout_factor $timeout_factor {
	# Now load the test binary.
	gdb_file_cmd $filename
    }

    # Generate an index file.
    set dir2 [standard_output_file "index_2"]
    remote_exec host "mkdir -p ${dir2}"
    with_timeout_factor $timeout_factor {
	gdb_test_no_output "save gdb-index $dir2" \
	    "create second gdb-index file"

	gdb_test_no_output "save gdb-index -dwarf-5 $dir2" \
	    "create second dwarf-index files"
    }

    # Close GDB.
    gdb_exit

    # Now check that the index files are identical.
    foreach suffix { gdb-index debug_names debug_str } {
	set result \
	    [remote_exec host \
		 "cmp -s \"$dir1/${index_filename_base}.${suffix}\" \"$dir2/${index_filename_base}.${suffix}\""]
	gdb_assert { [lindex $result 0] == 0 } \
	    "$suffix files are identical"
    }
}