[Bug gdb/28093] New: set language unknown -> print "foo" -> GDB crash

[Bug gdb/28093] New: set language unknown -> print "foo" -> GDB crash

[pedro at palves dot net]

https://sourceware.org/bugzilla/show_bug.cgi?id=28093

            Bug ID: 28093
           Summary: set language unknown -> print "foo" -> GDB crash
           Product: gdb
           Version: unknown
            Status: NEW
          Severity: normal
          Priority: P2
         Component: gdb
          Assignee: unassigned at sourceware dot org
          Reporter: pedro at palves dot net
  Target Milestone: ---

(gdb) set language unknown 
(gdb) p "foo"
Aborted (core dumped)

Thread 1 "gdb" received signal SIGSEGV, Segmentation fault.
parse_exp_in_context (stringptr=0x7fffffffd370, pc=0x0, block=0x0, comma=0,
void_context_p=false, tracker=0x7fffffffd270, cstate=0x0) at
/home/pedro/gdb/binutils-gdb/src/gdb/parse.c:522
522       result->op->set_outermost ();

(top-gdb) p result->op
$1 = std::unique_ptr<expr::operation> = {get() = 0x0}
(top-gdb) p result
$2 = std::unique_ptr<expression> = {get() = 0x5555564dbcd0}
(top-gdb) p *result
$3 = {language_defn = 0x55555649ea90 <unknown_language_defn>, gdbarch =
0x55555659e5e0, op = std::unique_ptr<expr::operation> = {get() = 0x0}}

(top-gdb) bt
#0  parse_exp_in_context (stringptr=0x7fffffffd370, pc=0x0, block=0x0, comma=0,
void_context_p=false, tracker=0x7fffffffd270, cstate=0x0) at
/home/pedro/gdb/binutils-gdb/src/gdb/parse.c:522
#1  0x0000555555b03f20 in parse_expression (During symbol reading: .debug_line
address at offset 0x48fdc7 is 0 [in module
/home/pedro/gdb/binutils-gdb/build/gdb/gdb]
string=0x5555564db182 "\"foo\"", tracker=0x0, void_context_p=false) at
/home/pedro/gdb/binutils-gdb/src/gdb/parse.c:546
#2  0x0000555555b09762 in process_print_command_args (args=0x5555564db182
"\"foo\"", print_opts=0x7fffffffd450, voidprint=true) at
/home/pedro/gdb/binutils-gdb/src/gdb/printcmd.c:1304
#3  0x0000555555b0982d in print_command_1 (args=0x5555564db182 "\"foo\"",
voidprint=1) at /home/pedro/gdb/binutils-gdb/src/gdb/printcmd.c:1318
#4  0x0000555555b09c72 in print_command (exp=0x5555564db182 "\"foo\"",
from_tty=1) at /home/pedro/gdb/binutils-gdb/src/gdb/printcmd.c:1435
#5  0x00005555557a0164 in do_const_cfunc (c=0x55555654a610, args=0x5555564db182
"\"foo\"", from_tty=1) at
/home/pedro/gdb/binutils-gdb/src/gdb/cli/cli-decode.c:102
#6  0x00005555557a4a38 in cmd_func (cmd=0x55555654a610, args=0x5555564db182
"\"foo\"", from_tty=1) at
/home/pedro/gdb/binutils-gdb/src/gdb/cli/cli-decode.c:2160
#7  0x0000555555cbfdc2 in execute_command (p=0x5555564db186 "\"", from_tty=1)
at /home/pedro/gdb/binutils-gdb/src/gdb/top.c:674
#8  0x000055555592494b in command_handler (command=0x5555564db180 "p \"foo\"")
at /home/pedro/gdb/binutils-gdb/src/gdb/event-top.c:588
#9  0x0000555555924dd3 in command_line_handler (rl=...) at
/home/pedro/gdb/binutils-gdb/src/gdb/event-top.c:773
#10 0x0000555555cef958 in tui_command_line_handler (rl=...) at
/home/pedro/gdb/binutils-gdb/src/gdb/tui/tui-interp.c:268
#11 0x0000555555923fe4 in gdb_rl_callback_handler (rl=0x5555564dc340 "p
\"foo\"") at /home/pedro/gdb/binutils-gdb/src/gdb/event-top.c:218
#12 0x0000555555dd1342 in rl_callback_read_char () at
/home/pedro/gdb/binutils-gdb/src/readline/readline/callback.c:281
#13 0x0000555555923e00 in gdb_rl_callback_read_char_wrapper_noexcept () at
/home/pedro/gdb/binutils-gdb/src/gdb/event-top.c:176
#14 0x0000555555923eae in gdb_rl_callback_read_char_wrapper
(client_data=0x5555564daeb0) at
/home/pedro/gdb/binutils-gdb/src/gdb/event-top.c:193
#15 0x000055555592474b in stdin_event_handler (error=0,
client_data=0x5555564daeb0) at
/home/pedro/gdb/binutils-gdb/src/gdb/event-top.c:515
#16 0x0000555555f16c27 in handle_file_event (file_ptr=0x555556659160,
ready_mask=1) at /home/pedro/gdb/binutils-gdb/src/gdbsupport/event-loop.cc:575
#17 0x0000555555f171d9 in gdb_wait_for_event (block=1) at
/home/pedro/gdb/binutils-gdb/src/gdbsupport/event-loop.cc:701
#18 0x0000555555f15f84 in gdb_do_one_event () at
/home/pedro/gdb/binutils-gdb/src/gdbsupport/event-loop.cc:237
#19 0x0000555555a74503 in start_event_loop () at
/home/pedro/gdb/binutils-gdb/src/gdb/main.c:421
#20 0x0000555555a7464e in captured_command_loop () at
/home/pedro/gdb/binutils-gdb/src/gdb/main.c:481
#21 0x0000555555a760b5 in captured_main (data=0x7fffffffdb30) at
/home/pedro/gdb/binutils-gdb/src/gdb/main.c:1353
#22 0x0000555555a76127 in gdb_main (args=0x7fffffffdb30) at
/home/pedro/gdb/binutils-gdb/src/gdb/main.c:1368
#23 0x000055555563fd16 in main (argc=2, argv=0x7fffffffdc48) at
/home/pedro/gdb/binutils-gdb/src/gdb/gdb.c:32

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[Bug gdb/28093] set language unknown -> print "foo" -> GDB crash

[pedro at palves dot net]

https://sourceware.org/bugzilla/show_bug.cgi?id=28093

Pedro Alves <pedro at palves dot net> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |tromey at sourceware dot org

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[Bug gdb/28093] set language unknown -> print "foo" -> GDB crash

[tromey at sourceware dot org]

https://sourceware.org/bugzilla/show_bug.cgi?id=28093

Tom Tromey <tromey at sourceware dot org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Assignee|unassigned at sourceware dot org   |tromey at sourceware dot org

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[Bug gdb/28093] set language unknown -> print "foo" -> GDB crash

[tromey at sourceware dot org]

https://sourceware.org/bugzilla/show_bug.cgi?id=28093

Tom Tromey <tromey at sourceware dot org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Target Milestone|---                         |11.1

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[Bug gdb/28093] set language unknown -> print "foo" -> GDB crash

[tromey at sourceware dot org]

https://sourceware.org/bugzilla/show_bug.cgi?id=28093

--- Comment #1 from Tom Tromey <tromey at sourceware dot org> ---
Not technically a regression, I suppose.
Fedora 32 /bin/gdb:

(gdb) print "hi"
../../gdb/parse.c:725: internal-error: int prefixify_expression(expression*,
int): Assertion `expr->nelts > 0' failed.
A problem internal to GDB has been detected,
further debugging may prove unreliable.
Quit this debugging session? (y or n) 


The default language "parser" just does:

  int parser (struct parser_state *ps) const override
  {
    /* No parsing is done, just claim success.  */
    return 1;
  }

... which is pretty lame / wrong.

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[Bug gdb/28093] set language unknown -> print "foo" -> GDB crash

[tromey at sourceware dot org]

https://sourceware.org/bugzilla/show_bug.cgi?id=28093

--- Comment #2 from Tom Tromey <tromey at sourceware dot org> ---
https://sourceware.org/pipermail/gdb-patches/2021-July/180972.html

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[Bug gdb/28093] set language unknown -> print "foo" -> GDB crash

[cvs-commit at gcc dot gnu.org]

https://sourceware.org/bugzilla/show_bug.cgi?id=28093

--- Comment #3 from cvs-commit at gcc dot gnu.org <cvs-commit at gcc dot gnu.org> ---
The master branch has been updated by Tom Tromey <tromey@sourceware.org>:

https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;h=dcd482c1b756d9da2130552a6eb58b852d6efb97

commit dcd482c1b756d9da2130552a6eb58b852d6efb97
Author: Tom Tromey <tromey@adacore.com>
Date:   Thu Jul 15 10:13:18 2021 -0600

    Avoid expression parsing crash with unknown language

    PR gdb/28093 points out that gdb crashes when language is set to
    "unknown" and expression parsing is attempted.  At first I thought
    this was a regression due to the expression rewrite, but it turns out
    that older versions crash as well.

    This patch avoids the crash by changing the default expression parser
    to throw an exception.  I think this is preferable -- the current
    behavior of silently doing nothing does not really make sense.

    Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=28093

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[Bug gdb/28093] set language unknown -> print "foo" -> GDB crash

[cvs-commit at gcc dot gnu.org]

https://sourceware.org/bugzilla/show_bug.cgi?id=28093

--- Comment #4 from cvs-commit at gcc dot gnu.org <cvs-commit at gcc dot gnu.org> ---
The gdb-11-branch branch has been updated by Tom Tromey
<tromey@sourceware.org>:

https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;h=e22715ce300957aabdf908a76fb1bf8bc17bba21

commit e22715ce300957aabdf908a76fb1bf8bc17bba21
Author: Tom Tromey <tromey@adacore.com>
Date:   Thu Jul 15 10:13:18 2021 -0600

    Avoid expression parsing crash with unknown language

    PR gdb/28093 points out that gdb crashes when language is set to
    "unknown" and expression parsing is attempted.  At first I thought
    this was a regression due to the expression rewrite, but it turns out
    that older versions crash as well.

    This patch avoids the crash by changing the default expression parser
    to throw an exception.  I think this is preferable -- the current
    behavior of silently doing nothing does not really make sense.

    Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=28093
    (cherry picked from commit dcd482c1b756d9da2130552a6eb58b852d6efb97)

    gdb/ChangeLog
    2021-07-19  Tom Tromey  <tromey@adacore.com>

            PR gdb/28093
            * language.c (auto_or_unknown_language::parser): Call error.

    gdb/testsuite/ChangeLog
    2021-07-19  Tom Tromey  <tromey@adacore.com>

            PR gdb/28093
            * gdb.base/langs.exp: Add tests.

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[Bug gdb/28093] set language unknown -> print "foo" -> GDB crash

[tromey at sourceware dot org]

https://sourceware.org/bugzilla/show_bug.cgi?id=28093

Tom Tromey <tromey at sourceware dot org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |RESOLVED
         Resolution|---                         |FIXED

--- Comment #5 from Tom Tromey <tromey at sourceware dot org> ---
Fixed for gdb 11.

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