As reported in PR 27157, if some environment variables read at startup
by GDB are defined but empty, we hit the assert in gdb_abspath:
$ XDG_CACHE_HOME= ./gdb -nx --data-directory=data-directory -q
AddressSanitizer:DEADLYSIGNAL
=================================================================
==2007040==ERROR: AddressSanitizer: SEGV on unknown address 0x0000000001b0 (pc 0x5639d4aa4127 bp 0x7ffdac232c00 sp 0x7ffdac232bf0 T0)
==2007040==The signal is caused by a READ memory access.
==2007040==Hint: address points to the zero page.
#0 0x5639d4aa4126 in target_stack::top() const /home/smarchi/src/binutils-gdb/gdb/target.h:1334
#1 0x5639d4aa41f1 in inferior::top_target() /home/smarchi/src/binutils-gdb/gdb/inferior.h:369
#2 0x5639d4a70b1f in current_top_target() /home/smarchi/src/binutils-gdb/gdb/target.c:120
#3 0x5639d4b00591 in gdb_readline_wrapper_cleanup::gdb_readline_wrapper_cleanup() /home/smarchi/src/binutils-gdb/gdb/top.c:1046
#4 0x5639d4afab31 in gdb_readline_wrapper(char const*) /home/smarchi/src/binutils-gdb/gdb/top.c:1104
#5 0x5639d4ccce2c in defaulted_query /home/smarchi/src/binutils-gdb/gdb/utils.c:893
#6 0x5639d4ccd6af in query(char const*, ...) /home/smarchi/src/binutils-gdb/gdb/utils.c:985
#7 0x5639d4ccaec1 in internal_vproblem /home/smarchi/src/binutils-gdb/gdb/utils.c:373
#8 0x5639d4ccb3d1 in internal_verror(char const*, int, char const*, __va_list_tag*) /home/smarchi/src/binutils-gdb/gdb/utils.c:439
#9 0x5639d5151a92 in internal_error(char const*, int, char const*, ...) /home/smarchi/src/binutils-gdb/gdbsupport/errors.cc:55
#10 0x5639d5162ab4 in gdb_abspath(char const*) /home/smarchi/src/binutils-gdb/gdbsupport/pathstuff.cc:132
#11 0x5639d5162fac in get_standard_cache_dir[abi:cxx11]() /home/smarchi/src/binutils-gdb/gdbsupport/pathstuff.cc:228
#12 0x5639d3e76a81 in _initialize_index_cache() /home/smarchi/src/binutils-gdb/gdb/dwarf2/index-cache.c:325
#13 0x5639d4dbbe92 in initialize_all_files() /home/smarchi/build/binutils-gdb/gdb/init.c:321
#14 0x5639d4b00259 in gdb_init(char*) /home/smarchi/src/binutils-gdb/gdb/top.c:2344
#15 0x5639d4440715 in captured_main_1 /home/smarchi/src/binutils-gdb/gdb/main.c:950
#16 0x5639d444252e in captured_main /home/smarchi/src/binutils-gdb/gdb/main.c:1229
#17 0x5639d44425cf in gdb_main(captured_main_args*) /home/smarchi/src/binutils-gdb/gdb/main.c:1254
#18 0x5639d3923371 in main /home/smarchi/src/binutils-gdb/gdb/gdb.c:32
#19 0x7fa002d3f0b2 in __libc_start_main (/lib/x86_64-linux-gnu/libc.so.6+0x270b2)
#20 0x5639d392314d in _start (/home/smarchi/build/binutils-gdb/gdb/gdb+0x4d414d)
gdb_abspath doesn't handle empty strings, so handle this case in the
callers. If a variable is defined but empty, I think it's reasonable in
this case to just ignore it, as if it was not defined.
Note that this sometimes also lead to a segfault, because the failed
assertion happens very early during startup, before things are fully
initialized.
gdbsupport/ChangeLog:
PR gdb/27157
* pathstuff.cc (get_standard_cache_dir, get_standard_config_dir,
find_gdb_home_config_file): Add empty string check.
gdb/testsuite/ChangeLog:
PR gdb/27157
* gdb.base/empty-host-env-vars.exp: New test.
Change-Id: I8654d8e97e74e1dff6d308c111ae4b1bbf07bef9
This is a helper library that is used by gdb and gdbserver.
To send patches, follow the gdb patch submission instructions in
../gdb/CONTRIBUTE. For maintainers, see ../gdb/MAINTAINERS.
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