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Published 20 hours ago • verified publisher icon vadimcn

Weird evaluation of char arrays inside a struct (native expressions)

Open panourgue opened this issue 3 years ago • 3 comments

OS: macOS 11.3.1 (20E241) VSCode version: 1.56.2 Extension version: 1.6.3 Compiler: Apple clang version 12.0.5 (C/C++) Build target: x86_64-apple-macosx11.0.0

(Better see the screenshot – I fail at English) In the watch window I get weird evaluation of a sized char arrays inside a struct if I refer to the struct by pointer (native expressions). Same thing inside the locals window looks fine.

Screenshot 2021-05-26 at 14 50 19

Example code:

#include <string.h>
#include <stdlib.h>

typedef struct SomeStruct {
    char chars[100];
} SomeStruct;

int main(int argc, char const *argv[]) {
    SomeStruct* foo = (SomeStruct*)malloc(sizeof(SomeStruct));
    strcpy(foo->chars, "hello!");

    return 0;
}

Value of "lldb.dereferencePointers" doesn't seem to matter.

Excerpts from debug log:

  • locals window:

    "evaluateName":"foo.chars","name":"chars","type":"char [100]","value":""hello!"","variablesReference":1017`

  • watch window:

    "evaluateName":"foo.chars","name":"chars","type":"char [100]","value":""\xf0B@"","variablesReference":1018`

Debug log
configuration: {
  name: 'Launch',
  type: 'lldb',
  request: 'launch',
  program: '${workspaceFolder}/main',
  expressions: 'native',
  args: [],
  __configurationTarget: 5,
  relativePathBase: '/Volumes/Crucial/projects/3rd_party/vscode/plugins/vadimcn_vscode_lldb/bug_reports/watch_window_char_eval'
}
liblldb: /Users/anpan/.vscode/extensions/vadimcn.vscode-lldb-1.6.3/lldb/lib/liblldb.dylib
environment: {}
params: { evaluateForHovers: true, commandCompletions: true }
Listening on port 51738
[2021-05-26T12:04:09.777Z DEBUG codelldb] New debug session
INFO(Python) 15:04:10 formatters: Initializing
INFO(Python) 15:04:10 formatters.rust: Initializing
[2021-05-26T12:04:10.065Z DEBUG codelldb::dap_codec] --> {"command":"initialize","arguments":{"clientID":"vscode","clientName":"Visual Studio Code","adapterID":"lldb","pathFormat":"path","linesStartAt1":true,"columnsStartAt1":true,"supportsVariableType":true,"supportsVariablePaging":true,"supportsRunInTerminalRequest":true,"locale":"en-gb","supportsProgressReporting":true,"supportsInvalidatedEvent":true},"type":"request","seq":1}
[2021-05-26T12:04:10.065Z DEBUG codelldb::dap_codec]  {"command":"launch","arguments":{"name":"Launch","type":"lldb","request":"launch","program":"/Volumes/Crucial/projects/3rd_party/vscode/plugins/vadimcn_vscode_lldb/bug_reports/watch_window_char_eval/main","expressions":"native","args":[],"__configurationTarget":5,"relativePathBase":"/Volumes/Crucial/projects/3rd_party/vscode/plugins/vadimcn_vscode_lldb/bug_reports/watch_window_char_eval","_adapterSettings":{"displayFormat":"auto","showDisassembly":"auto","dereferencePointers":false,"suppressMissingSourceFiles":true,"evaluationTimeout":5,"consoleMode":"commands","sourceLanguages":null,"terminalPromptClear":null,"evaluateForHovers":true,"commandCompletions":true},"__sessionId":"33c0edd5-7bb1-4ab0-a332-aec19e672dae"},"type":"request","seq":2}
[2021-05-26T12:04:10.069Z DEBUG codelldb::dap_codec]  {"command":"setBreakpoints","arguments":{"source":{"name":"main.c","path":"/Volumes/Crucial/projects/3rd_party/vscode/plugins/vadimcn_vscode_lldb/bug_reports/watch_window_char_eval/main.c"},"lines":[16],"breakpoints":[{"line":16}],"sourceModified":false},"type":"request","seq":3}
[2021-05-26T12:04:10.076Z DEBUG codelldb::dap_codec]  {"type":"response","seq":4,"command":"runInTerminal","request_seq":3,"success":true,"body":{"shellProcessId":26985}}
[2021-05-26T12:04:10.086Z DEBUG codelldb::dap_codec] --> {"command":"setFunctionBreakpoints","arguments":{"breakpoints":[]},"type":"request","seq":5}
[2021-05-26T12:04:10.087Z DEBUG codelldb::dap_codec]  {"command":"setDataBreakpoints","arguments":{"breakpoints":[]},"type":"request","seq":6}
[2021-05-26T12:04:10.097Z DEBUG codelldb::dap_codec]  {"command":"setExceptionBreakpoints","arguments":{"filters":["cpp_throw"]},"type":"request","seq":7}
[2021-05-26T12:04:10.105Z DEBUG codelldb::dap_codec]  {"command":"configurationDone","type":"request","seq":8}
[2021-05-26T12:04:10.111Z DEBUG codelldb::dap_codec]  {"command":"threads","type":"request","seq":9}
[2021-05-26T12:04:10.441Z DEBUG codelldb::dap_codec] [2021-05-26T12:04:10.502Z DEBUG codelldb::debug_session] Debug event: 0x7fc971d8f5e0 Event: broadcaster = 0x7fc973114050 (lldb.process), type = 0x00000001 (state-changed), data = { process = 0x7fc973114018 (pid = 27740), state = stopped}
[2021-05-26T12:04:10.502Z DEBUG codelldb::dap_codec] <-- {"type":"event","seq":52,"event":"stopped","body":{"allThreadsStopped":true,"reason":"breakpoint","threadId":262705}}
[2021-05-26T12:04:10.511Z DEBUG codelldb::dap_codec] --> {"command":"threads","type":"request","seq":10}
[2021-05-26T12:04:10.511Z DEBUG codelldb::dap_codec] <-- {"type":"response","request_seq":10,"success":true,"command":"threads","body":{"threads":[{"id":262705,"name":"1: tid=262705"}]}}
[2021-05-26T12:04:10.513Z DEBUG codelldb::dap_codec] --> {"command":"stackTrace","arguments":{"threadId":262705,"startFrame":0,"levels":1},"type":"request","seq":11}
[2021-05-26T12:04:10.514Z DEBUG codelldb::dap_codec] <-- {"type":"response","request_seq":11,"success":true,"command":"stackTrace","body":{"stackFrames":[{"column":5,"id":1001,"line":16,"name":"main","source":{"name":"main.c","path":"/Volumes/Crucial/projects/3rd_party/vscode/plugins/vadimcn_vscode_lldb/bug_reports/watch_window_char_eval/main.c"}}],"totalFrames":2}}
[2021-05-26T12:04:10.924Z DEBUG codelldb::dap_codec] --> {"command":"scopes","arguments":{"frameId":1001},"type":"request","seq":12}
[2021-05-26T12:04:10.924Z DEBUG codelldb::dap_codec] <-- {"type":"response","request_seq":12,"success":true,"command":"scopes","body":{"scopes":[{"expensive":false,"name":"Local","variablesReference":1002},{"expensive":false,"name":"Static","variablesReference":1003},{"expensive":false,"name":"Global","variablesReference":1004},{"expensive":false,"name":"Registers","variablesReference":1005}]}}
[2021-05-26T12:04:10.930Z DEBUG codelldb::dap_codec] --> {"command":"variables","arguments":{"variablesReference":1002},"type":"request","seq":13}
[2021-05-26T12:04:10.937Z DEBUG codelldb::dap_codec] --> {"command":"stackTrace","arguments":{"threadId":262705,"startFrame":1,"levels":19},"type":"request","seq":14}
[2021-05-26T12:04:10.940Z DEBUG codelldb::dap_codec] <-- {"type":"response","request_seq":13,"success":true,"command":"variables","body":{"variables":[{"evaluateName":"argc","name":"argc","type":"int","value":"1","variablesReference":0},{"evaluateName":"argv","name":"argv","type":"const char **","value":"0x00007ffeefbff4e0","variablesReference":1006},{"evaluateName":"foo","name":"foo","type":"SomeStruct *","value":"0x00000001004042f0","variablesReference":1007}]}}
[2021-05-26T12:04:10.940Z DEBUG codelldb::disassembly] libdyld.dylib`start + 1
[2021-05-26T12:04:10.940Z DEBUG codelldb::dap_codec] <-- {"type":"response","request_seq":14,"success":true,"command":"stackTrace","body":{"stackFrames":[{"column":0,"id":1008,"line":4,"name":"start","presentationHint":"subtle","source":{"name":"@start","sourceReference":1000}}],"totalFrames":2}}
[2021-05-26T12:04:12.951Z DEBUG codelldb::dap_codec] --> {"command":"variables","arguments":{"variablesReference":1007},"type":"request","seq":15}
[2021-05-26T12:04:12.951Z DEBUG codelldb::dap_codec] <-- {"type":"response","request_seq":15,"success":true,"command":"variables","body":{"variables":[{"evaluateName":"foo.chars","name":"chars","type":"char [100]","value":""hello!"","variablesReference":1009}]}}
[2021-05-26T12:04:15.430Z DEBUG codelldb::dap_codec] --> {"command":"evaluate","arguments":{"expression":"foo","frameId":1001,"context":"watch"},"type":"request","seq":16}
[2021-05-26T12:04:15.430Z DEBUG codelldb::dap_codec] --> {"command":"scopes","arguments":{"frameId":1001},"type":"request","seq":17}
[2021-05-26T12:04:15.648Z DEBUG codelldb::debug_session] Debug event: 0x7fc971c814d8 Event: broadcaster = 0x7fc9729ed440 (lldb.target), type = 0x00000002 (modules-loaded), data = {__lldb_apple_objc_v2_get_dynamic_class_info2}
[2021-05-26T12:04:15.648Z DEBUG codelldb::dap_codec] <-- {"type":"response","request_seq":17,"success":true,"command":"scopes","body":{"scopes":[{"expensive":false,"name":"Local","variablesReference":1011},{"expensive":false,"name":"Static","variablesReference":1012},{"expensive":false,"name":"Global","variablesReference":1013},{"expensive":false,"name":"Registers","variablesReference":1014}]}}
[2021-05-26T12:04:15.648Z DEBUG codelldb::debug_session] Debug event: 0x7fc951c10018 Event: broadcaster = 0x7fc9729ed440 (lldb.target), type = 0x00000002 (modules-loaded), data = {__lldb_caller_function}
[2021-05-26T12:04:15.648Z DEBUG codelldb::dap_codec] <-- {"type":"event","seq":53,"event":"module","body":{"module":{"id":"__lldb_apple_objc_v2_get_dynamic_class_info2","name":"__lldb_apple_objc_v2_get_dynamic_class_info2","path":"__lldb_apple_objc_v2_get_dynamic_class_info2","symbolStatus":"Symbols not found"},"reason":"new"}}
[2021-05-26T12:04:15.648Z DEBUG codelldb::dap_codec] <-- {"type":"event","seq":54,"event":"module","body":{"module":{"id":"__lldb_caller_function","name":"__lldb_caller_function","path":"__lldb_caller_function","symbolStatus":"Symbols not found"},"reason":"new"}}
[2021-05-26T12:04:15.648Z DEBUG codelldb::debug_session] Debug event: 0x7fc971fd9ae8 Event: broadcaster = 0x7fc9729ed440 (lldb.target), type = 0x00000002 (modules-loaded), data = {__lldb_apple_objc_v2_get_shared_cache_class_info}
[2021-05-26T12:04:15.648Z DEBUG codelldb::debug_session] Debug event: 0x7fc971fdcce8 Event: broadcaster = 0x7fc9729ed440 (lldb.target), type = 0x00000002 (modules-loaded), data = {__lldb_caller_function}
[2021-05-26T12:04:15.648Z DEBUG codelldb::dap_codec] <-- {"type":"event","seq":55,"event":"module","body":{"module":{"id":"__lldb_apple_objc_v2_get_shared_cache_class_info","name":"__lldb_apple_objc_v2_get_shared_cache_class_info","path":"__lldb_apple_objc_v2_get_shared_cache_class_info","symbolStatus":"Symbols not found"},"reason":"new"}}
[2021-05-26T12:04:15.648Z DEBUG codelldb::dap_codec] <-- {"type":"event","seq":56,"event":"module","body":{"module":{"id":"__lldb_caller_function","name":"__lldb_caller_function","path":"__lldb_caller_function","symbolStatus":"Symbols not found"},"reason":"new"}}
[2021-05-26T12:04:15.648Z DEBUG codelldb::dap_codec] <-- {"type":"response","request_seq":16,"success":true,"command":"evaluate","body":{"result":"0x00000001004042f0","type":"SomeStruct *","variablesReference":1010}}
[2021-05-26T12:04:15.651Z DEBUG codelldb::dap_codec] --> {"command":"variables","arguments":{"variablesReference":1011},"type":"request","seq":18}
[2021-05-26T12:04:15.651Z DEBUG codelldb::dap_codec] <-- {"type":"response","request_seq":18,"success":true,"command":"variables","body":{"variables":[{"evaluateName":"argc","name":"argc","type":"int","value":"1","variablesReference":0},{"evaluateName":"argv","name":"argv","type":"const char **","value":"0x00007ffeefbff4e0","variablesReference":1015},{"evaluateName":"foo","name":"foo","type":"SomeStruct *","value":"0x00000001004042f0","variablesReference":1016}]}}
[2021-05-26T12:04:15.655Z DEBUG codelldb::dap_codec] --> {"command":"variables","arguments":{"variablesReference":1016},"type":"request","seq":19}
[2021-05-26T12:04:15.656Z DEBUG codelldb::dap_codec] <-- {"type":"response","request_seq":19,"success":true,"command":"variables","body":{"variables":[{"evaluateName":"foo.chars","name":"chars","type":"char [100]","value":""hello!"","variablesReference":1017}]}}
[2021-05-26T12:04:17.418Z DEBUG codelldb::dap_codec] --> {"command":"variables","arguments":{"variablesReference":1010},"type":"request","seq":20}
[2021-05-26T12:04:17.418Z DEBUG codelldb::dap_codec] <-- {"type":"response","request_seq":20,"success":true,"command":"variables","body":{"variables":[{"evaluateName":"foo.chars","name":"chars","type":"char [100]","value":""\xf0B@"","variablesReference":1018}]}}

panourgue avatar May 26 '21 12:05 panourgue

Sorry for the barrage of "reports" 🥺

panourgue avatar May 26 '21 12:05 panourgue

Looks like a LLDB bug: I can reproduce it in the CLI version as well:

(lldb) expr --ptr-depth=1 -- foo
(SomeStruct *) $39 = 0x00005555555592a0 {
  chars = "\xa0\x92UUUU"
}

vadimcn avatar May 28 '21 16:05 vadimcn

Sorry about that. I only checked:

(lldb) p foo->chars
(char [100]) $14 = "hello!"

Which obviously works. Didn't know that is not how you get stuff from lldb, my bad.

panourgue avatar May 29 '21 03:05 panourgue