Data breakpoints not working properly

[chroberino]

Hi! I’ve been testing the recently introduced data breakpoints feature. Creating a data breakpoint appears to succeed, but pressing Continue immediately fails with GDB warnings and the session stops.

Steps to Reproduce

1. Start a debug session against the remote target.
2. Set a normal source breakpoint (works and hits).
3. Obtain the address of a variable
4. Add a data breakpoint via the Command Palette on that address.
   (Adapter sends -break-watch -a *(0x94411c4); GDB reports hw-awpt={number="2"}.)
5. Press Continue.

Actual Behavior

• Continue fails and the session stops with warnings logged from GDB:

  Warning:
  Could not insert hardware watchpoint 2.
  Could not insert hardware breakpoints:
  You may have requested too many hardware breakpoints/watchpoints.
  

• GDB returns error,msg="Command aborted." and the adapter reports a stopped event with reason "error".

Expected Behavior

• Program should continue with the watchpoint armed and only stop on the configured data access (read/write).
• If the target cannot arm a hardware watchpoint, the adapter should either:
  • fall back (optionally) to a software watchpoint, or
  • provide a clear, actionable error explaining why the watchpoint can’t be armed and how to adjust (e.g., reduce threads, change access type/size, or align the address/length).

Detailed Logs

1. Adding a normal breakpoint on a line of code:

From client: setBreakpoints({"source":{"name":"Main.c","path":"d:\\DbgTest\\Main.c"},"lines":[22],"breakpoints":[{"line":22}],"sourceModified":false})
GDB command: 12 -data-evaluate-expression "$_gthread"
GDB write command: 12 -data-evaluate-expression "$_gthread"
GDB result: 12 done,value="1"
GDB command: 12 -data-evaluate-expression "$_gthread" completed with data
GDB command: 13 -exec-interrupt --all
GDB write command: 13 -exec-interrupt --all
GDB result: 13 done
GDB command: 13 -exec-interrupt --all completed with data
To client: {"seq":0,"type":"event","event":"output","body":{"category":"stdout","output":"\nThread "}}

Thread To client: {"seq":0,"type":"event","event":"output","body":{"category":"stdout","output":"1 received signal SIGTRAP, Trace/breakpoint trap.\n"}}
1 received signal SIGTRAP, Trace/breakpoint trap.
To client: {"seq":0,"type":"event","event":"output","body":{"category":"stdout","output":"0x77a36e6c in ?? ()\n"}}
0x77a36e6c in ?? ()
GDB exec async: stopped,reason="signal-received",signal-name="SIGTRAP",signal-meaning="Trace/breakpoint trap",frame={addr="0x77a36e6c",func="??",args=[],arch="i386"},thread-id="1",stopped-threads="all"
GDB command: 14 -break-list
GDB write command: 14 -break-list
GDB result: 14 done,BreakpointTable={nr_rows="0",nr_cols="6",hdr=[{width="7",alignment="-1",col_name="number",colhdr="Num"},{width="14",alignment="-1",col_name="type",colhdr="Type"},{width="4",alignment="-1",col_name="disp",colhdr="Disp"},{width="3",alignment="-1",col_name="enabled",colhdr="Enb"},{width="10",alignment="-1",col_name="addr",colhdr="Address"},{width="40",alignment="2",col_name="what",colhdr="What"}],body=[]}
GDB command: 14 -break-list completed with data
GDB command: 15 -break-insert --source "d:\\DbgTest\\Main.c" --line 22
GDB write command: 15 -break-insert --source "d:\\DbgTest\\Main.c" --line 22
GDB result: 15 done,bkpt={number="1",type="breakpoint",disp="keep",enabled="y",addr="0x0949c938",func="ProgramCyclic",file="d:/DbgTest/Main.c",fullname="d:\\DbgTest\\Main.c",line="22",thread-groups=["i1"],times="0",original-location="-source d:\\DbgTest\\Main.c -line 22"}
GDB command: 15 -break-insert --source "d:\\DbgTest\\Main.c" --line 22 completed with data
To client: {"seq":0,"type":"response","request_seq":8,"command":"setBreakpoints","success":true,"body":{"breakpoints":[{"id":1,"line":22,"verified":true}]}}
GDB command: 16 -exec-continue
GDB write command: 16 -exec-continue
GDB result: 16 running
GDB command: 16 -exec-continue completed with data
GDB exec async: running,thread-id="all"
To client: {"seq":0,"type":"event","event":"continued","body":{"threadId":1,"allThreadsContinued":true}}
GDB notify async: breakpoint-modified,bkpt={number="1",type="breakpoint",disp="keep",enabled="y",addr="0x0949c938",func="ProgramCyclic",file="d:/DbgTest/Main.c",fullname="d:\\DbgTest\\Main.c",line="22",thread-groups=["i1"],times="1",original-location="-source d:\\DbgTest\\Main.c -line 22"}
To client: {"seq":0,"type":"event","event":"breakpoint","body":{"reason":"changed","breakpoint":{"id":1,"verified":true,"source":{"name":"d:\\DbgTest\\Main.c","path":"d:/DbgTest/Main.c"},"line":22}}}
To client: {"seq":0,"type":"event","event":"output","body":{"category":"stdout","output":"[Switching to Thread 313]\n"}}
[Switching to Thread 313]
To client: {"seq":0,"type":"event","event":"output","body":{"category":"stdout","output":"\n"}}

To client: {"seq":0,"type":"event","event":"output","body":{"category":"stdout","output":"Thread 8 hit Breakpoint 1, ProgramCyclic () at d:/DbgTest/Main.c:22\n"}}
Thread 8 hit Breakpoint 1, ProgramCyclic () at d:/DbgTest/Main.c:22
To client: {"seq":0,"type":"event","event":"output","body":{"category":"stdout","output":"22\t\tlong result = 0; \n"}}
22		long result = 0;
GDB exec async: stopped,reason="breakpoint-hit",disp="keep",bkptno="1",frame={addr="0x0949c938",func="ProgramCyclic",args=[],file="d:/DbgTest/Main.c",fullname="d:\\DbgTest\\Main.c",line="22",arch="i386"},thread-id="8",stopped-threads="all"
To client: {"seq":0,"type":"event","event":"stopped","body":{"reason":"breakpoint","allThreadsStopped":true,"threadId":8}}
From client: threads(undefined)
GDB command: 17 -thread-info
GDB write command: 17 -thread-info
GDB result: 17 done,threads=[{id="1",target-id="Thread 224",frame={level="0",addr="0x77a36e6c",func="??",args=[],arch="i386"},state="stopped"},{id="2",target-id="Thread 225",frame={level="0",addr="0x77a36e6c",func="??",args=[],arch="i386"},state="stopped"},{id="3",target-id="Thread 226",frame={level="0",addr="0x77a36e6c",func="??",args=[],arch="i386"},state="stopped"},{id="4",target-id="Thread 285",frame={level="0",addr="0x77a36e6c",func="??",args=[],arch="i386"},state="stopped"},{id="5",target-id="Thread 293",frame={level="0",addr="0x77a36e6c",func="??",args=[],arch="i386"},state="stopped"},{id="6",target-id="Thread 299",frame={level="0",addr="0x77a36e6c",func="??",args=[],arch="i386"},state="stopped"},{id="7",target-id="Thread 306",frame={level="0",addr="0x77a36e6c",func="??",args=[],arch="i386"},state="stopped"},{id="8",target-id="Thread 313",frame={level="0",addr="0x0949c938",func="ProgramCyclic",args=[],file="d:/DbgTest/Main.c",fullname="d:\\DbgTest\\Mai
GDB -cont-: 17 n.c",line="22",arch="i386"},state="stopped"},{id="9",target-id="Thread 320",frame={level="0",addr="0x77a36e6c",func="??",args=[],arch="i386"},state="stopped"},{id="10",target-id="Thread 327",frame={level="0",addr="0x77a36e6c",func="??",args=[],arch="i386"},state="stopped"},{id="11",target-id="Thread 334",frame={level="0",addr="0x77a36e6c",func="??",args=[],arch="i386"},state="stopped"},{id="12",target-id="Thread 341",frame={level="0",addr="0x77a36e6c",func="??",args=[],arch="i386"},state="stopped"},{id="13",target-id="Thread 956",frame={level="0",addr="0x77a3718c",func="??",args=[],arch="i386"},state="stopped"},{id="14",target-id="Thread 959",frame={level="0",addr="0x77a36e6c",func="??",args=[],arch="i386"},state="stopped"},{id="15",target-id="Thread 1012",frame={level="0",addr="0x77a36e6c",func="??",args=[],arch="i386"},state="stopped"},{id="16",target-id="Thread 1018",frame={level="0",addr="0x77a36e6c",func="??",args=[],arch="i386"},state
GDB -cont-: 17 ="stopped"},{id="17",target-id="Thread 1020",frame={level="0",addr="0x77a36e6c",func="??",args=[],arch="i386"},state="stopped"},{id="18",target-id="Thread 1021",frame={level="0",addr="0x00000000",func="??",args=[],arch="i386"},state="stopped"},{id="19",target-id="Thread 1024",frame={level="0",addr="0x77a3718c",func="??",args=[],arch="i386"},state="stopped"},{id="20",target-id="Thread 1033",frame={level="0",addr="0x77a3718c",func="??",args=[],arch="i386"},state="stopped"},{id="21",target-id="Thread 1086",frame={level="0",addr="0x77a36e6c",func="??",args=[],arch="i386"},state="stopped"},{id="22",target-id="Thread 1087",frame={level="0",addr="0x77a36e6c",func="??",args=[],arch="i386"},state="stopped"},{id="23",target-id="Thread 1089",frame={level="0",addr="0x77a36e6c",func="??",args=[],arch="i386"},state="stopped"},{id="24",target-id="Thread 1137",frame={level="0",addr="0x77a36e6c",func="??",args=[],arch="i386"},state="stopped"},{id="25",target-id="Thread 1161",frame={level="0",addr="0x77
GDB -cont-: 17 a36e6c",func="??",args=[],arch="i386"},state="stopped"},{id="26",target-id="Thread 1162",frame={level="0",addr="0x77a36e6c",func="??",args=[],arch="i386"},state="stopped"},{id="27",target-id="Thread 1163",frame={level="0",addr="0x77a36e6c",func="??",args=[],arch="i386"},state="stopped"},{id="28",target-id="Thread 1164",frame={level="0",addr="0x77a36e6c",func="??",args=[],arch="i386"},state="stopped"},{id="29",target-id="Thread 1165",frame={level="0",addr="0x77a36e6c",func="??",args=[],arch="i386"},state="stopped"},{id="30",target-id="Thread 1166",frame={level="0",addr="0x77a36e6c",func="??",args=[],arch="i386"},state="stopped"},{id="31",target-id="Thread 1167",frame={level="0",addr="0x77a36e6c",func="??",args=[],arch="i386"},state="stopped"},{id="32",target-id="Thread 1168",frame={level="0",addr="0x77a36e6c",func="??",args=[],arch="i386"},state="stopped"},{id="33",target-id="Thread 1169",frame={level="0",addr="0x77a36e6c",func="??",args=[],arch="i386"},state="stopped"},{id="34",target-
GDB -cont-: 17 id="Thread 1180",frame={level="0",addr="0x77a3718c",func="??",args=[],arch="i386"},state="stopped"}],current-thread-id="8"
GDB command: 17 -thread-info completed with data
To client: {"seq":0,"type":"response","request_seq":9,"command":"threads","success":true,"body":{"threads":[{"id":1,"name":"1","running":false},{"id":2,"name":"2","running":false},{"id":3,"name":"3","running":false},{"id":4,"name":"4","running":false},{"id":5,"name":"5","running":false},{"id":6,"name":"6","running":false},{"id":7,"name":"7","running":false},{"id":8,"name":"8","running":false},{"id":9,"name":"9","running":false},{"id":10,"name":"10","running":false},{"id":11,"name":"11","running":false},{"id":12,"name":"12","running":false},{"id":13,"name":"13","running":false},{"id":14,"name":"14","running":false},{"id":15,"name":"15","running":false},{"id":16,"name":"16","running":false},{"id":17,"name":"17","running":false},{"id":18,"name":"18","running":false},{"id":19,"name":"19","running":false},{"id":20,"name":"20","running":false},{"id":21,"name":"21","running":false},{"id":22,"name":"22","running":false},{"id":23,"name":"23","running":false},{"id":24,"name":"24","running":false},{"id":25,"name":"25","running":false},{"id":26,"name":"26","running":false},{"id":27,"name":"27","running":false},{"id":28,"name":"28","running":false},{"id":29,"name":"29","running":false},{"id":30,"name":"30","running":false},{"id":31,"name":"31","running":false},{"id":32,"name":"32","running":false},{"id":33,"name":"33","running":false},{"id":34,"name":"34","running":false}]}}
From client: stackTrace({"threadId":8,"startFrame":0,"levels":20})
GDB command: 18 -stack-info-depth --thread 8 100
GDB write command: 18 -stack-info-depth --thread 8 100
GDB result: 18 done,depth="3"
GDB command: 18 -stack-info-depth --thread 8 100 completed with data
GDB command: 19 -stack-list-frames --thread 8 0 2
GDB write command: 19 -stack-list-frames --thread 8 0 2
GDB result: 19 done,stack=[frame={level="0",addr="0x0949c938",func="ProgramCyclic",file="d:/DbgTest/Main.c",fullname="d:\\DbgTest\\Main.c",line="22",arch="i386"},frame={level="1",addr="0x00486b02",func="??",arch="i386"},frame={level="2",addr="0x00000000",func="??",arch="i386"}]
GDB command: 19 -stack-list-frames --thread 8 0 2 completed with data
To client: {"seq":0,"type":"response","request_seq":10,"command":"stackTrace","success":true,"body":{"stackFrames":[{"id":1000,"source":{"name":"Main.c","path":"d:\\DbgTest\\Main.c","sourceReference":0},"line":22,"column":0,"name":"ProgramCyclic","instructionPointerReference":"0x0949c938"},{"id":1001,"line":0,"column":0,"name":"??","instructionPointerReference":"0x00486b02"},{"id":1002,"line":0,"column":0,"name":"??","instructionPointerReference":"0x00000000"}],"totalFrames":3}}
From client: evaluate({"expression":"AutoState","frameId":1000,"context":"watch"})
GDB command: 20 -stack-info-depth --thread 8 100
GDB write command: 20 -stack-info-depth --thread 8 100
From client: evaluate({"expression":"gInfeedUp","frameId":1000,"context":"watch"})
GDB command: 21 -stack-info-depth --thread 8 100
GDB write command: 21 -stack-info-depth --thread 8 100
From client: evaluate({"expression":"result","frameId":1000,"context":"watch"})
GDB command: 22 -stack-info-depth --thread 8 100
GDB write command: 22 -stack-info-depth --thread 8 100
From client: evaluate({"expression":"&RunOld","frameId":1000,"context":"watch"})
GDB command: 23 -stack-info-depth --thread 8 100
GDB write command: 23 -stack-info-depth --thread 8 100
GDB result: 20 done,depth="3"
GDB command: 20 -stack-info-depth --thread 8 100 completed with data
GDB command: 24 -var-create --thread 8 --frame 0 - * "AutoState"
GDB write command: 24 -var-create --thread 8 --frame 0 - * "AutoState"
GDB result: 21 done,depth="3"
GDB command: 21 -stack-info-depth --thread 8 100 completed with data
GDB result: 22 done,depth="3"
GDB command: 22 -stack-info-depth --thread 8 100 completed with data
GDB result: 23 done,depth="3"
GDB command: 23 -stack-info-depth --thread 8 100 completed with data
GDB command: 25 -var-create --thread 8 --frame 0 - * "gInfeedUp"
GDB write command: 25 -var-create --thread 8 --frame 0 - * "gInfeedUp"
GDB command: 26 -var-create --thread 8 --frame 0 - * "result"
GDB write command: 26 -var-create --thread 8 --frame 0 - * "result"
GDB command: 27 -var-create --thread 8 --frame 0 - * "&RunOld"
GDB write command: 27 -var-create --thread 8 --frame 0 - * "&RunOld"
GDB result: 24 done,name="var1",numchild="0",value="AUTO_IDLE",type="AutoStateEnum",has_more="0"
GDB command: 24 -var-create --thread 8 --frame 0 - * "AutoState" completed with data
To client: {"seq":0,"type":"response","request_seq":11,"command":"evaluate","success":true,"body":{"result":"AUTO_IDLE","type":"AutoStateEnum","variablesReference":0}}
GDB result: 25 done,name="var2",numchild="3",value="{...}",type="InfeedUpIFType",has_more="0"
GDB command: 25 -var-create --thread 8 --frame 0 - * "gInfeedUp" completed with data
To client: {"seq":0,"type":"response","request_seq":12,"command":"evaluate","success":true,"body":{"result":"{...}","type":"InfeedUpIFType","variablesReference":1000}}
GDB result: 26 done,name="var3",numchild="0",value="80146008",type="long",thread-id="8",has_more="0"
GDB command: 26 -var-create --thread 8 --frame 0 - * "result" completed with data
To client: {"seq":0,"type":"response","request_seq":13,"command":"evaluate","success":true,"body":{"result":"80146008","type":"long","variablesReference":0}}
GDB result: 27 done,name="var4",numchild="1",value="0x94411c4 <RunOld>",type="BOOL *",has_more="0"
GDB command: 27 -var-create --thread 8 --frame 0 - * "&RunOld" completed with data
To client: {"seq":0,"type":"response","request_seq":14,"command":"evaluate","success":true,"body":{"result":"0x94411c4 <RunOld>","type":"BOOL *","variablesReference":1001}}
From client: scopes({"frameId":1000})
To client: {"seq":0,"type":"response","request_seq":15,"command":"scopes","success":true,"body":{"scopes":[{"name":"Local","variablesReference":1002,"expensive":false},{"name":"Registers","variablesReference":1003,"expensive":true}]}}
From client: variables({"variablesReference":1002})
GDB command: 28 -stack-info-depth --thread 8 100
GDB write command: 28 -stack-info-depth --thread 8 100
GDB result: 28 done,depth="3"
GDB command: 28 -stack-info-depth --thread 8 100 completed with data
GDB command: 29 -stack-list-variables --thread 8 --frame 0 --simple-values
GDB write command: 29 -stack-list-variables --thread 8 --frame 0 --simple-values
GDB result: 29 done,variables=[{name="result",type="long",value="80146008"}]
GDB command: 29 -stack-list-variables --thread 8 --frame 0 --simple-values completed with data
GDB command: 30 -var-update 1 var3
GDB write command: 30 -var-update 1 var3
GDB result: 30 done,changelist=[]
GDB command: 30 -var-update 1 var3 completed with data
To client: {"seq":0,"type":"response","request_seq":16,"command":"variables","success":true,"body":{"variables":[{"name":"result","evaluateName":"result","value":"80146008","type":"long","memoryReference":"&(result)","variablesReference":0}]}}

2. Adding a data breakpoint (via command palette):

From client: dataBreakpointInfo({"name":"&RunOld"})
GDB command: 31 -symbol-info-functions --name ^&RunOld$
GDB write command: 31 -symbol-info-functions --name ^&RunOld$
GDB result: 31 done,symbols={}
GDB command: 31 -symbol-info-functions --name ^&RunOld$ completed with data
GDB command: 32 -data-evaluate-expression "&&RunOld"
GDB write command: 32 -data-evaluate-expression "&&RunOld"
GDB result: 32 error,msg="A syntax error in expression, near `&&RunOld'."
GDB command: 32 -data-evaluate-expression "&&RunOld" failed with 'A syntax error in expression, near `&&RunOld'.'
To client: {"seq":0,"type":"response","request_seq":17,"command":"dataBreakpointInfo","success":true,"body":{"dataId":null,"description":"No data breakpoint for &RunOld"}}
From client: evaluate({"expression":"&RunOld","frameId":1000,"context":"watch"})
GDB command: 33 -stack-info-depth --thread 8 100
GDB write command: 33 -stack-info-depth --thread 8 100
GDB result: 33 done,depth="3"
GDB command: 33 -stack-info-depth --thread 8 100 completed with data
GDB command: 34 -var-update 1 var4
GDB write command: 34 -var-update 1 var4
GDB result: 34 done,changelist=[]
GDB command: 34 -var-update 1 var4 completed with data
To client: {"seq":0,"type":"response","request_seq":18,"command":"evaluate","success":true,"body":{"result":"0x94411c4 <RunOld>","type":"BOOL *","variablesReference":1004}}
From client: dataBreakpointInfo({"name":"&RunOld"})
GDB command: 35 -symbol-info-functions --name ^&RunOld$
GDB write command: 35 -symbol-info-functions --name ^&RunOld$
GDB result: 35 done,symbols={}
GDB command: 35 -symbol-info-functions --name ^&RunOld$ completed with data
GDB command: 36 -data-evaluate-expression "&&RunOld"
GDB write command: 36 -data-evaluate-expression "&&RunOld"
GDB result: 36 error,msg="A syntax error in expression, near `&&RunOld'."
GDB command: 36 -data-evaluate-expression "&&RunOld" failed with 'A syntax error in expression, near `&&RunOld'.'
To client: {"seq":0,"type":"response","request_seq":19,"command":"dataBreakpointInfo","success":true,"body":{"dataId":null,"description":"No data breakpoint for &RunOld"}}
From client: dataBreakpointInfo({"name":"0x94411c4","bytes":1,"asAddress":true})
To client: {"seq":0,"type":"response","request_seq":20,"command":"dataBreakpointInfo","success":true,"body":{"dataId":"0x94411c4","description":"Data breakpoint for 0x94411c4","accessTypes":["read","write","readWrite"],"canPersist":true}}
From client: dataBreakpointInfo({"name":"0x94411c4","bytes":1,"asAddress":true})
To client: {"seq":0,"type":"response","request_seq":21,"command":"dataBreakpointInfo","success":true,"body":{"dataId":"0x94411c4","description":"Data breakpoint for 0x94411c4","accessTypes":["read","write","readWrite"],"canPersist":true}}
From client: setDataBreakpoints({"breakpoints":[{"dataId":"0x94411c4","accessType":"readWrite"}]})
GDB command: 37 -break-list
GDB write command: 37 -break-list
GDB result: 37 done,BreakpointTable={nr_rows="1",nr_cols="6",hdr=[{width="7",alignment="-1",col_name="number",colhdr="Num"},{width="14",alignment="-1",col_name="type",colhdr="Type"},{width="4",alignment="-1",col_name="disp",colhdr="Disp"},{width="3",alignment="-1",col_name="enabled",colhdr="Enb"},{width="10",alignment="-1",col_name="addr",colhdr="Address"},{width="40",alignment="2",col_name="what",colhdr="What"}],body=[bkpt={number="1",type="breakpoint",disp="keep",enabled="y",addr="0x0949c938",func="ProgramCyclic",file="d:/DbgTest/Main.c",fullname="d:\\DbgTest\\Main.c",line="22",thread-groups=["i1"],times="1",original-location="-source d:\\DbgTest\\Main.c -line 22"}]}
GDB command: 37 -break-list completed with data
GDB command: 38 -break-watch -a *(0x94411c4)
GDB write command: 38 -break-watch -a *(0x94411c4)
GDB result: 38 done,hw-awpt={number="2",exp="*(0x94411c4)"}
GDB command: 38 -break-watch -a *(0x94411c4) completed with data
GDB command: 39 -break-list
GDB write command: 39 -break-list
GDB result: 39 done,BreakpointTable={nr_rows="2",nr_cols="6",hdr=[{width="7",alignment="-1",col_name="number",colhdr="Num"},{width="14",alignment="-1",col_name="type",colhdr="Type"},{width="4",alignment="-1",col_name="disp",colhdr="Disp"},{width="3",alignment="-1",col_name="enabled",colhdr="Enb"},{width="10",alignment="-1",col_name="addr",colhdr="Address"},{width="40",alignment="2",col_name="what",colhdr="What"}],body=[bkpt={number="1",type="breakpoint",disp="keep",enabled="y",addr="0x0949c938",func="ProgramCyclic",file="d:/DbgTest/Main.c",fullname="d:\\DbgTest\\Main.c",line="22",thread-groups=["i1"],times="1",original-location="-source d:\\DbgTest\\Main.c -line 22"},bkpt={number="2",type="acc watchpoint",disp="keep",enabled="y",what="*(0x94411c4)",thread-groups=["i1"],times="0",original-location="*(0x94411c4)"}]}
GDB command: 39 -break-list completed with data
To client: {"seq":0,"type":"response","request_seq":22,"command":"setDataBreakpoints","success":true,"body":{"breakpoints":[{"verified":true,"id":2}]}}

3. Pressing "continue" in the dbug controls:

From client: continue({"threadId":8})
GDB command: 40 -exec-continue --thread 8
GDB write command: 40 -exec-continue --thread 8
GDB result: 40 running
GDB command: 40 -exec-continue --thread 8 completed with data
GDB exec async: running,thread-id="all"
To client: {"seq":0,"type":"event","event":"continued","body":{"threadId":1,"allThreadsContinued":true}}
To client: {"seq":0,"type":"response","request_seq":23,"command":"continue","success":true,"body":{"allThreadsContinued":true}}
To client: {"seq":0,"type":"event","event":"output","body":{"category":"log","output":"Warning:\n"}}
Warning:
To client: {"seq":0,"type":"event","event":"output","body":{"category":"log","output":"Could not insert hardware watchpoint 2.\n"}}
Could not insert hardware watchpoint 2.
To client: {"seq":0,"type":"event","event":"output","body":{"category":"log","output":"Could not insert hardware breakpoints:\n"}}
Could not insert hardware breakpoints:
To client: {"seq":0,"type":"event","event":"output","body":{"category":"log","output":"You may have requested too many hardware breakpoints/watchpoints.\n"}}
You may have requested too many hardware breakpoints/watchpoints.
To client: {"seq":0,"type":"event","event":"output","body":{"category":"log","output":"\n"}}

GDB result: 40 error,msg="Command aborted."
GDB response with no command: 40
To client: {"seq":0,"type":"event","event":"stopped","body":{"reason":"error","allThreadsStopped":true,"threadId":1}}
From client: threads(undefined)
GDB command: 41 -thread-info
GDB write command: 41 -thread-info
GDB result: 41 done,threads=[{id="1",target-id="Thread 224",frame={level="0",addr="0x77a36e6c",func="??",args=[],arch="i386"},state="stopped"},{id="2",target-id="Thread 225",frame={level="0",addr="0x77a36e6c",func="??",args=[],arch="i386"},state="stopped"},{id="3",target-id="Thread 226",frame={level="0",addr="0x77a36e6c",func="??",args=[],arch="i386"},state="stopped"},{id="4",target-id="Thread 285",frame={level="0",addr="0x77a36e6c",func="??",args=[],arch="i386"},state="stopped"},{id="5",target-id="Thread 293",frame={level="0",addr="0x77a36e6c",func="??",args=[],arch="i386"},state="stopped"},{id="6",target-id="Thread 299",frame={level="0",addr="0x77a36e6c",func="??",args=[],arch="i386"},state="stopped"},{id="7",target-id="Thread 306",frame={level="0",addr="0x77a36e6c",func="??",args=[],arch="i386"},state="stopped"},{id="8",target-id="Thread 313",frame={level="0",addr="0x0949c938",func="ProgramCyclic",args=[],file="d:/DbgTest/Main.c",fullname="d:\\DbgTest\\Mai
GDB -cont-: 41 n.c",line="22",arch="i386"},state="stopped"},{id="9",target-id="Thread 320",frame={level="0",addr="0x77a36e6c",func="??",args=[],arch="i386"},state="stopped"},{id="10",target-id="Thread 327",frame={level="0",addr="0x77a36e6c",func="??",args=[],arch="i386"},state="stopped"},{id="11",target-id="Thread 334",frame={level="0",addr="0x77a36e6c",func="??",args=[],arch="i386"},state="stopped"},{id="12",target-id="Thread 341",frame={level="0",addr="0x77a36e6c",func="??",args=[],arch="i386"},state="stopped"},{id="13",target-id="Thread 956",frame={level="0",addr="0x77a3718c",func="??",args=[],arch="i386"},state="stopped"},{id="14",target-id="Thread 959",frame={level="0",addr="0x77a36e6c",func="??",args=[],arch="i386"},state="stopped"},{id="15",target-id="Thread 1012",frame={level="0",addr="0x77a36e6c",func="??",args=[],arch="i386"},state="stopped"},{id="16",target-id="Thread 1018",frame={level="0",addr="0x77a36e6c",func="??",args=[],arch="i386"},state
GDB -cont-: 41 ="stopped"},{id="17",target-id="Thread 1020",frame={level="0",addr="0x77a36e6c",func="??",args=[],arch="i386"},state="stopped"},{id="18",target-id="Thread 1021",frame={level="0",addr="0x00000000",func="??",args=[],arch="i386"},state="stopped"},{id="19",target-id="Thread 1024",frame={level="0",addr="0x77a3718c",func="??",args=[],arch="i386"},state="stopped"},{id="20",target-id="Thread 1033",frame={level="0",addr="0x77a3718c",func="??",args=[],arch="i386"},state="stopped"},{id="21",target-id="Thread 1086",frame={level="0",addr="0x77a36e6c",func="??",args=[],arch="i386"},state="stopped"},{id="22",target-id="Thread 1087",frame={level="0",addr="0x77a36e6c",func="??",args=[],arch="i386"},state="stopped"},{id="23",target-id="Thread 1089",frame={level="0",addr="0x77a36e6c",func="??",args=[],arch="i386"},state="stopped"},{id="24",target-id="Thread 1137",frame={level="0",addr="0x77a36e6c",func="??",args=[],arch="i386"},state="stopped"},{id="25",target-id="Thread 1161",frame={level="0",addr="0x77
GDB -cont-: 41 a36e6c",func="??",args=[],arch="i386"},state="stopped"},{id="26",target-id="Thread 1162",frame={level="0",addr="0x77a36e6c",func="??",args=[],arch="i386"},state="stopped"},{id="27",target-id="Thread 1163",frame={level="0",addr="0x77a36e6c",func="??",args=[],arch="i386"},state="stopped"},{id="28",target-id="Thread 1164",frame={level="0",addr="0x77a36e6c",func="??",args=[],arch="i386"},state="stopped"},{id="29",target-id="Thread 1165",frame={level="0",addr="0x77a36e6c",func="??",args=[],arch="i386"},state="stopped"},{id="30",target-id="Thread 1166",frame={level="0",addr="0x77a36e6c",func="??",args=[],arch="i386"},state="stopped"},{id="31",target-id="Thread 1167",frame={level="0",addr="0x77a36e6c",func="??",args=[],arch="i386"},state="stopped"},{id="32",target-id="Thread 1168",frame={level="0",addr="0x77a36e6c",func="??",args=[],arch="i386"},state="stopped"},{id="33",target-id="Thread 1169",frame={level="0",addr="0x77a36e6c",func="??",args=[],arch="i386"},state="stopped"},{id="34",target-
GDB -cont-: 41 id="Thread 1180",frame={level="0",addr="0x77a3718c",func="??",args=[],arch="i386"},state="stopped"}],current-thread-id="8"
GDB command: 41 -thread-info completed with data
To client: {"seq":0,"type":"response","request_seq":24,"command":"threads","success":true,"body":{"threads":[{"id":1,"name":"1","running":false},{"id":2,"name":"2","running":false},{"id":3,"name":"3","running":false},{"id":4,"name":"4","running":false},{"id":5,"name":"5","running":false},{"id":6,"name":"6","running":false},{"id":7,"name":"7","running":false},{"id":8,"name":"8","running":false},{"id":9,"name":"9","running":false},{"id":10,"name":"10","running":false},{"id":11,"name":"11","running":false},{"id":12,"name":"12","running":false},{"id":13,"name":"13","running":false},{"id":14,"name":"14","running":false},{"id":15,"name":"15","running":false},{"id":16,"name":"16","running":false},{"id":17,"name":"17","running":false},{"id":18,"name":"18","running":false},{"id":19,"name":"19","running":false},{"id":20,"name":"20","running":false},{"id":21,"name":"21","running":false},{"id":22,"name":"22","running":false},{"id":23,"name":"23","running":false},{"id":24,"name":"24","running":false},{"id":25,"name":"25","running":false},{"id":26,"name":"26","running":false},{"id":27,"name":"27","running":false},{"id":28,"name":"28","running":false},{"id":29,"name":"29","running":false},{"id":30,"name":"30","running":false},{"id":31,"name":"31","running":false},{"id":32,"name":"32","running":false},{"id":33,"name":"33","running":false},{"id":34,"name":"34","running":false}]}}
From client: stackTrace({"threadId":1,"startFrame":0,"levels":20})
GDB command: 42 -stack-info-depth --thread 1 100
GDB write command: 42 -stack-info-depth --thread 1 100
GDB result: 42 done,depth="4"
GDB command: 42 -stack-info-depth --thread 1 100 completed with data
GDB command: 43 -stack-list-frames --thread 1 0 3
GDB write command: 43 -stack-list-frames --thread 1 0 3
GDB result: 43 done,stack=[frame={level="0",addr="0x77a36e6c",func="??",arch="i386"},frame={level="1",addr="0x767c7478",func="??",arch="i386"},frame={level="2",addr="0x00000730",func="??",arch="i386"},frame={level="3",addr="0x00000000",func="??",arch="i386"}]
GDB command: 43 -stack-list-frames --thread 1 0 3 completed with data
To client: {"seq":0,"type":"response","request_seq":25,"command":"stackTrace","success":true,"body":{"stackFrames":[{"id":1000,"line":0,"column":0,"name":"??","instructionPointerReference":"0x77a36e6c"},{"id":1001,"line":0,"column":0,"name":"??","instructionPointerReference":"0x767c7478"},{"id":1002,"line":0,"column":0,"name":"??","instructionPointerReference":"0x00000730"},{"id":1003,"line":0,"column":0,"name":"??","instructionPointerReference":"0x00000000"}],"totalFrames":4}}
From client: stackTrace({"threadId":8,"startFrame":0,"levels":20})
GDB command: 44 -stack-info-depth --thread 8 100
GDB write command: 44 -stack-info-depth --thread 8 100
GDB result: 44 done,depth="3"
GDB command: 44 -stack-info-depth --thread 8 100 completed with data
GDB command: 45 -stack-list-frames --thread 8 0 2
GDB write command: 45 -stack-list-frames --thread 8 0 2
GDB result: 45 done,stack=[frame={level="0",addr="0x0949c938",func="ProgramCyclic",file="d:/DbgTest/Main.c",fullname="d:\\DbgTest\\Main.c",line="22",arch="i386"},frame={level="1",addr="0x00486b02",func="??",arch="i386"},frame={level="2",addr="0x00000000",func="??",arch="i386"}]
GDB command: 45 -stack-list-frames --thread 8 0 2 completed with data
To client: {"seq":0,"type":"response","request_seq":26,"command":"stackTrace","success":true,"body":{"stackFrames":[{"id":1004,"source":{"name":"Main.c","path":"d:\\DbgTest\\Main.c","sourceReference":0},"line":22,"column":0,"name":"ProgramCyclic","instructionPointerReference":"0x0949c938"},{"id":1005,"line":0,"column":0,"name":"??","instructionPointerReference":"0x00486b02"},{"id":1006,"line":0,"column":0,"name":"??","instructionPointerReference":"0x00000000"}],"totalFrames":3}}

[jreineckearm]

Thanks for raising this, @chroberino .

We need to see what we can realistically do about this on adapter level. Every target architecture may handle data breakpoints differently. And may have limited resource. So, we rely a lot on how the GDB server handles this. Most of the messages you see come either from GDB or the GDB server as they are. @omarArm , please correct me if I am wrong.

Also, GDB unfortunately has the habit to allow as many breakpoints (code and data) as you set. And only tries to install them in the target system on the next continue (or comparable). If that fails, it aborts the run with the above error message which indeed is quite vague.

Making suggestions on what to fix with your setup is then again highly dependent on the target architecture. As an example: Arm v7-M watchpoints have some constraints on supported start addresses and on sizes (must be a power of 2) of watch ranges. Which are lifted in the Arm v8-M architecture version. So, ideally a GDB server would give adequate suggestions when it fails.

You mentioned software watchpoints....can you please help us to understand how these would behave?

@omarArm , can you please have a look if there is anything we can do to make this a little smoother in terms of better, generic error messages? Except from that I am afraid some of this feedback needs to be directed either to GDB or the maintainers of the GDB server you are using.

[chroberino]

Thanks for the clarification, @jreineckearm!

Regarding software watchpoints: these are implemented entirely by GDB (not the target CPU). Instead of using hardware debug registers, GDB emulates the behavior by repeatedly reading and comparing the watched memory location as the program runs. If the value changes between checks, GDB stops execution.

Official GDB documentation: https://sourceware.org/gdb/current/onlinedocs/gdb.html/Set-Watchpoints.html

In practice:

• They don’t rely on target hardware, so they work even if no hardware watchpoints are available.
• They are much slower, because GDB must single-step or monitor memory changes in software.
• On remote targets, they usually only work if the GDB server supports single-step execution and memory inspection between steps -- otherwise they’re ineffective.

So, I only mentioned them as a potential fallback mechanism -- something that could theoretically be offered if a hardware data breakpoint fails, though it’s likely impractical for most embedded or remote debugging scenarios.

[omarArm]

@jreineckearm I will have a look at the piece of code that prints the error message and change it to something meaningful, sure no problem. However, I am not entirely sure why did the issue of too many breakpoints/watchpoints happened in your case since you only have a single breakpoint and a single watchpoint.

@chroberino Does your hardware not support watchpoints at all maybe?

[chroberino]

Thanks @jreineckearm and @omarArm, and apologies for the confusion!
It turns out the GDB server build I was using simply didn’t support watchpoints.
After switching to a different build, data breakpoints now work as expected.

Also, just to clarify: I originally assumed the command “Add Data Breakpoint at Address” was contributed by cdt-gdb-vscode, but I’ve since learned that this command is actually provided by VS Code itself -- and unfortunately it’s not available in Theia! So there is currently no way to use data breakpoints in Theia.

Thanks again for your time and for the helpful explanations! 🙏

[chroberino]

FYI, I have created a Theia feature request for data breakpoints: eclipse-theia/theia#16445

[omarArm]

Hi @chroberino no worries at all, these things happen. Thanks for pointing me to updating the error message, I am sure this will be useful for future users nonetheless

[chroberino]

@jreineckearm, @omarArm,I have another observation regarding data breakpoints that might be relevant for documentation or might indicate an issue in the way watchpoints are set up by the adapter.

Scenario
I tested data breakpoints (“Break When Value Is Read”) on four variables located in adjacent memory addresses:

• varA (type short, address 0x93e2da2)
• varB (type short, address 0x93e2da4)
• varC (type bool, address 0x93e2da6)
• varD (type bool, address 0x93e2da7)

All four variables are contiguous in memory.

Steps to Reproduce:

1. Start a debug session.
2. Set a read data breakpoint for varA (address 0x93e2da2).
3. Set a read data breakpoint for varB (address 0x93e2da4).
4. Set a read data breakpoint for varC (address 0x93e2da6).
5. Set a read data breakpoint for varD (address 0x93e2da7).
6. Access the variables individually during program execution and observe which breakpoints trigger.

Observed Behavior:

• The data breakpoint for 0x93e2da2 (varA) halts only when varA is read (as expected).
• The data breakpoint for 0x93e2da4 (varB) halts when varB, varC, or varD are read (unexpected).
• The data breakpoint for 0x93e2da6 (varC) halts when either varC or varD is read (unexpected).
• The data breakpoint for 0x93e2da7 (varD) halts only when varD is read (as expected).

Expected Behavior:
Each data breakpoint should trigger only when the specific memory address or variable it was set for is accessed.
Adjacent variables should not influence one another.

Interpretation:
This looks like watchpoints are realized on aligned multi-byte regions (e.g. 2/4 bytes), so a watch starting at 0x93e2da4 could cover up to 0x93e2da7.

Questions:

1. Is this overlapping behavior expected given typical GDB/GDB-server watchpoint granularity/alignment rules?
2. If yes, is there any room in cdt-gdb-adapter to influence the effective watch size/granularity (e.g. via how expressions are issued), or is this strictly determined by the GDB server/target?
3. If it’s server-determined, would you recommend documenting this limitation/behavior for users so they understand possible overlaps with adjacent addresses?

[omarArm]

@chroberino Thank you for your questions, they really do help in making this solution better.

So the size of a watchpoint is very dependent on the GDB-server and the underlying architecture being used, some GDB-servers and CPU architectures don't even support them. So to answer your question, I guess I will have to say "it depends".

In my honest opinion, I don't think the cdt-gdb-adapter would be the right place to influence the granularity issues, since really the possibilities are endless. I usually test new features with a couple of GDB servers and a couple of architectures, but then some users would have a GDB-server or a device which I have never even heard of.

That being said, I think mentioning this limitation in the documentation would be a good idea yes. I will do so shortly and please let me know if you have any further questions.