d04ead7406
Currently GDB when executing in reverse over multiple statements in a single
line of source code, GDB stops in the middle of the line. Thus requiring
multiple commands to reach the previous line. GDB should stop at the first
instruction of the line, not in the middle of the line.
The following description of the incorrect behavior was taken from an
earlier message by Pedro Alves <pedro@palves.net>:
https://sourceware.org/pipermail/gdb-patches/2023-January/196110.html
---------------------------------
The source line looks like:
func1 (); func2 ();
in the test case:
(gdb) list 1
1 void func1 ()
2 {
3 }
4
5 void func2 ()
6 {
7 }
8
9 int main ()
10 {
11 func1 (); func2 ();
12 }
compiled with:
$ gcc reverse.c -o reverse -g3 -O0
$ gcc -v
...
gcc version 11.3.0 (Ubuntu 11.3.0-1ubuntu1~22.04)
Now let's debug it with target record, using current gdb git master
(f3d8ae90b2),
$ gdb ~/reverse
GNU gdb (GDB) 14.0.50.20230124-git
...
Reading symbols from /home/pedro/reverse...
(gdb) start
Temporary breakpoint 1 at 0x1147: file reverse.c, line 11.
Starting program: /home/pedro/reverse
[Thread debugging using libthread_db enabled]
Using host libthread_db library "/lib/x86_64-linux-gnu/libthread_db.so.1".
Temporary breakpoint 1, main () at reverse.c:11
11 func1 (); func2 ();
(gdb) record
(gdb) disassemble /s
Dump of assembler code for function main:
reverse.c:
10 {
0x000055555555513f <+0>: endbr64
0x0000555555555143 <+4>: push %rbp
0x0000555555555144 <+5>: mov %rsp,%rbp
11 func1 (); func2 ();
=> 0x0000555555555147 <+8>: mov $0x0,%eax
0x000055555555514c <+13>: call 0x555555555129 <func1>
0x0000555555555151 <+18>: mov $0x0,%eax
0x0000555555555156 <+23>: call 0x555555555134 <func2>
0x000055555555515b <+28>: mov $0x0,%eax
12 }
0x0000555555555160 <+33>: pop %rbp
0x0000555555555161 <+34>: ret
End of assembler dump.
(gdb) n
12 }
So far so good, a "next" stepped over the whole of line 11 and stopped at
line 12.
Let's confirm where we are now:
(gdb) disassemble /s
Dump of assembler code for function main:
reverse.c:
10 {
0x000055555555513f <+0>: endbr64
0x0000555555555143 <+4>: push %rbp
0x0000555555555144 <+5>: mov %rsp,%rbp
11 func1 (); func2 ();
0x0000555555555147 <+8>: mov $0x0,%eax
0x000055555555514c <+13>: call 0x555555555129 <func1>
0x0000555555555151 <+18>: mov $0x0,%eax
0x0000555555555156 <+23>: call 0x555555555134 <func2>
0x000055555555515b <+28>: mov $0x0,%eax
12 }
=> 0x0000555555555160 <+33>: pop %rbp
0x0000555555555161 <+34>: ret
End of assembler dump.
Good, we're at the first instruction of line 12.
Now let's undo the "next", with "reverse-next":
(gdb) reverse-next
11 func1 (); func2 ();
Seemingly stopped at line 11. Let's see exactly where:
(gdb) disassemble /s
Dump of assembler code for function main:
reverse.c:
10 {
0x000055555555513f <+0>: endbr64
0x0000555555555143 <+4>: push %rbp
0x0000555555555144 <+5>: mov %rsp,%rbp
11 func1 (); func2 ();
0x0000555555555147 <+8>: mov $0x0,%eax
0x000055555555514c <+13>: call 0x555555555129 <func1>
=> 0x0000555555555151 <+18>: mov $0x0,%eax
0x0000555555555156 <+23>: call 0x555555555134 <func2>
0x000055555555515b <+28>: mov $0x0,%eax
12 }
0x0000555555555160 <+33>: pop %rbp
0x0000555555555161 <+34>: ret
End of assembler dump.
(gdb)
And lo, we stopped in the middle of line 11! That is a bug, we should have
stepped back all the way to the beginning of the line. The "reverse-next"
should have fully undone the prior "next" command.
--------------------
This patch fixes the incorrect GDB behavior by ensuring that GDB stops at
the first instruction in the line.
The test case gdb.reverse/func-map-to-same-line.exp is added to testsuite
to verify this fix when the line table information is and is not available.
204 lines
8.2 KiB
Text
204 lines
8.2 KiB
Text
# Copyright 2008-2023 Free Software Foundation, Inc.
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# This program is free software; you can redistribute it and/or modify
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# it under the terms of the GNU General Public License as published by
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# the Free Software Foundation; either version 3 of the License, or
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# (at your option) any later version.
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#
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# This program is distributed in the hope that it will be useful,
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# but WITHOUT ANY WARRANTY; without even the implied warranty of
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# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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# GNU General Public License for more details.
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#
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# You should have received a copy of the GNU General Public License
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# along with this program. If not, see <http://www.gnu.org/licenses/>. */
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# This file is part of the GDB testsuite. It tests reverse stepping.
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# Lots of code borrowed from "step-test.exp".
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# The reverse finish command should return from a function and stop on
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# the first instruction of the source line where the function call is made.
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# Specifically, the behavior should match doing a reverse next from the
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# first instruction in the function. GDB should only take one reverse step
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# or next statement to reach the previous source code line.
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# This testcase verifies the reverse-finish command stops at the first
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# instruction in the source code line where the function was called. There
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# are two scenarios that must be checked:
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# 1) gdb is at the entry point instruction for the function
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# 2) gdb is in the body of the function.
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# This test verifies the fix for gdb bugzilla:
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# https://sourceware.org/bugzilla/show_bug.cgi?id=29927
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# PowerPC supports two entry points to a function. The normal entry point
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# is called the local entry point (LEP). The alternate entry point is called
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# the global entry point (GEP). A function call via a function pointer
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# will entry via the GEP. A normal function call will enter via the LEP.
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#
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# This test has been expanded to include tests to verify the reverse-finish
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# command works properly if the function is called via the GEP. The original
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# test only verified the reverse-finish command for a normal call that used
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# the LEP.
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if ![supports_reverse] {
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return
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}
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standard_testfile
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if { [prepare_for_testing "failed to prepare" $testfile $srcfile] } {
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return -1
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}
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runto_main
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set target_remote [gdb_is_target_remote]
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if [supports_process_record] {
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# Activate process record/replay.
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gdb_test_no_output "record" "turn on process record for test1"
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}
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### TEST 1: reverse finish from the entry point instruction (LEP) in
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### function1 when called using the normal entry point (LEP).
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# Set breakpoint at call to function1 in main.
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set bp_LEP_test [gdb_get_line_number "CALL VIA LEP" $srcfile]
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gdb_breakpoint $srcfile:$bp_LEP_test temporary
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# Continue to break point at function1 call in main.
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gdb_continue_to_breakpoint \
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"stopped at function1 entry point instruction to stepi into function" \
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".*$srcfile:$bp_LEP_test\r\n.*"
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# stepi until we see "{" indicating we entered function1
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repeat_cmd_until "stepi" "CALL VIA LEP" "{" "stepi into function1 call" "100"
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# The reverse-finish command should stop on the function call instruction
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# which is the last instruction in the source code line. Another reverse-next
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# instruction stops at the previous source code line.
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gdb_test "reverse-finish" ".*function1 \\(a, b\\); // CALL VIA LEP.*" \
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"reverse-finish function1 LEP call from LEP "
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gdb_test "reverse-next" ".*b = 5;.*" "reverse next 2, at b = 5, call from LEP"
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gdb_test "reverse-continue" ".*" "setup for test 2"
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# Turn off record to clear logs and turn on again
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gdb_test "record stop" "Process record is stopped.*" \
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"turn off process record for test1"
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gdb_test_no_output "record" "turn on process record for test2"
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### TEST 2: reverse finish from the body of function1.
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# Set breakpoint at call to function1 in main.
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gdb_breakpoint $srcfile:$bp_LEP_test temporary
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# Continue to break point at function1 call in main.
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gdb_continue_to_breakpoint \
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"at function1 entry point instruction to step to body of function" \
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".*$srcfile:$bp_LEP_test\r\n.*"
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# do a step instruction to get to the body of the function
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gdb_test "step" ".*int ret = 0;.*" "step test 1"
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# The reverse-finish command should stop on the function call instruction
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# which is the last instruction in the source code line. Another reverse-next
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# instruction stops at the previous source code line.
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gdb_test "reverse-finish" ".*function1 \\(a, b\\); // CALL VIA LEP.*" \
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"reverse-finish function1 LEP call from function body"
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gdb_test "reverse-next" ".*b = 5;.*" \
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"reverse next 2 at b = 5, from function body"
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gdb_test "reverse-continue" ".*" "setup for test 3"
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# Turn off record to clear logs and turn on again
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gdb_test "record stop" "Process record is stopped.*" \
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"turn off process record for test2"
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gdb_test_no_output "record" "turn on process record for test3"
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### TEST 3: reverse finish from the alternate entry point instruction (GEP) in
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### function1 when called using the alternate entry point (GEP).
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# Set breakpoint at call to funp in main.
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set bp_GEP_test [gdb_get_line_number "CALL VIA GEP" $srcfile]
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gdb_breakpoint $srcfile:$bp_GEP_test temporary
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# Continue to break point at funp call in main.
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gdb_continue_to_breakpoint \
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"stopped at function1 entry point instruction to stepi into funp" \
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".*$srcfile:$bp_GEP_test\r\n.*"
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# stepi until we see "{" indicating we entered function.
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repeat_cmd_until "stepi" "CALL VIA GEP" "{" "stepi into funp call"
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# The reverse-finish command should stop on the function call instruction
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# which is the last instruction in the source code line. Another reverse-next
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# instruction stops at the previous source code line.
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gdb_test "reverse-finish" ".*funp \\(a, b\\);.*" \
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"function1 GEP call call from GEP"
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gdb_test "reverse-next" ".*b = 50;.*" "reverse next 2 at b = 50, call from GEP"
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gdb_test "reverse-continue" ".*" "setup for test 4"
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# Turn off record to clear logs and turn on again
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gdb_test "record stop" "Process record is stopped.*" \
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"turn off process record for test3"
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gdb_test_no_output "record" "turn on process record for test4"
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### TEST 4: reverse finish from between the GEP and LEP in
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### function1 when called using the alternate entry point (GEP).
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# Set breakpoint at call to funp in main.
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set bp_GEP_test [gdb_get_line_number "CALL VIA GEP" $srcfile]
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gdb_breakpoint $srcfile:$bp_GEP_test temporary
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# Continue to break point at funp call in main.
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gdb_continue_to_breakpoint \
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"stopped at function1 entry point instruction to stepi into funp again" \
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".*$srcfile:$bp_GEP_test\r\n.*"
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# stepi until we see "{" indicating we entered function.
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repeat_cmd_until "stepi" "CALL VIA GEP" "{" "stepi into funp call again"
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# do one more stepi so we are between the GEP and LEP.
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gdb_test "stepi" "{" "stepi to between GEP and LEP"
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# The reverse-finish command should stop on the function call instruction
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# which is the last instruction in the source code line. Another reverse-next
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# instruction stops at the previous source code line.
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gdb_test "reverse-finish" ".*funp \\(a, b\\);.*" \
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"function1 GEP call call from GEP again"
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gdb_test "reverse-next" ".*b = 50;.*" \
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"reverse next 2 at b = 50, call from GEP again"
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gdb_test "reverse-continue" ".*" "setup for test 5"
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# Turn off record to clear logs and turn on again
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gdb_test "record stop" "Process record is stopped.*" \
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"turn off process record for test4"
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gdb_test_no_output "record" "turn on process record for test5"
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### TEST 5: reverse finish from the body of function 1 when calling using the
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### alternate entrypoint (GEP).
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gdb_breakpoint $srcfile:$bp_GEP_test temporary
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# Continue to break point at funp call.
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gdb_continue_to_breakpoint \
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"at function1 entry point instruction to step to body of funp call" \
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".*$srcfile:$bp_GEP_test\r\n.*"
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# Step into body of funp, called via GEP.
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gdb_test "step" ".*int ret = 0;.*" "step test 2"
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# The reverse-finish command should stop on the function call instruction
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# which is the last instruction in the source code line. Another reverse-next
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# instruction stops at the previous source code line.
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gdb_test "reverse-finish" ".*funp \\(a, b\\);.*" \
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"reverse-finish function1 GEP call, from function body "
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gdb_test "reverse-next" ".*b = 50;.*" \
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"reverse next 2 at b = 50 from function body"
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