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From: "grantrwittmann at gmail dot com" <gcc-bugzilla@gcc.gnu.org> To: gcc-bugs@gcc.gnu.org Subject: [Bug c/112870] New: incorrect jmp when using goto on a function, causing infinite loop Date: Tue, 05 Dec 2023 18:41:30 +0000 [thread overview] Message-ID: <bug-112870-4@http.gcc.gnu.org/bugzilla/> (raw) https://gcc.gnu.org/bugzilla/show_bug.cgi?id=112870 Bug ID: 112870 Summary: incorrect jmp when using goto on a function, causing infinite loop Product: gcc Version: 13.2.0 Status: UNCONFIRMED Severity: normal Priority: P3 Component: c Assignee: unassigned at gcc dot gnu.org Reporter: grantrwittmann at gmail dot com Target Milestone: --- When first setting a variable to a label, then jumping after that label to a function (not calling the function), GCC generates incorrect assembly causing the goto statement to jump to the previous label and not the function. The code: void function() { return; } int main() { void* label_var = &&label; label: goto *&function; } compiles to this assembly: function: push rbp mov rbp, rsp nop pop rbp ret main: push rbp mov rbp, rsp mov QWORD PTR [rbp-8], OFFSET FLAT:.L4 .L4: nop jmp .L4 The last jmp goes back to .L4 (label) even though it should be going to function. The assembly is compiled correctly when the `label_var` declaration is removed. This same code compiles correctly on other compilers like clang (17.0.1): function: # @function push rbp mov rbp, rsp pop rbp ret main: # @main push rbp mov rbp, rsp mov dword ptr [rbp - 4], 0 lea rax, [rip + .Ltmp2] mov qword ptr [rbp - 16], rax .Ltmp2: # Block address taken .LBB1_1: # =>This Inner Loop Header: Depth=1 lea rax, [rip + function] mov qword ptr [rbp - 24], rax # 8-byte Spill jmp .LBB1_2 .LBB1_2: # in Loop: Header=BB1_1 Depth=1 mov rax, qword ptr [rbp - 24] # 8-byte Reload jmp rax All examples from this issue were compiled and ran through the godbolt.org online compiler explorer.
next reply other threads:[~2023-12-05 18:41 UTC|newest] Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top 2023-12-05 18:41 grantrwittmann at gmail dot com [this message] 2023-12-05 18:44 ` [Bug c/112870] " pinskia at gcc dot gnu.org 2023-12-05 19:01 ` grantrwittmann at gmail dot com 2023-12-05 19:04 ` pinskia at gcc dot gnu.org 2024-03-16 17:58 ` pinskia at gcc dot gnu.org
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