Add documentation for -Xtrace:maxstringlength option by Sreekala-Gopakumar · Pull Request #1497 · eclipse-openj9/openj9-docs

Sreekala-Gopakumar · 2025-03-20T18:57:26Z

Added the new parameter, maxstringlength.

Closes #1466
Signed-off-by: Sreekala Gopakumar sreekala.gopakumar@ibm.com

Sreekala-Gopakumar · 2025-03-20T18:59:55Z

Jenkins doc stage

Sreekala-Gopakumar · 2025-03-20T19:17:00Z

@h3110n3rv3 @pshipton - I have updated the topics. Please check and confirm that the information is correct. Could you please especially check the following:

examples given in https://eclipse-openj9.github.io/openj9-docs-staging/1497/xtrace/#maxstringlength
whether the new option is placed under the correct section i.e. https://eclipse-openj9.github.io/openj9-docs-staging/1497/xtrace/#configuring-trace
Can this be added as a new feature in the 0.50.0 release section - https://eclipse-openj9.github.io/openj9-docs-staging/1497/version0.50/ ?

Thanks!

pshipton · 2025-03-21T17:42:28Z

@h3110n3rv3 Pls do the initial review.

Can this be added as a new feature in the 0.50.0 release section

Yes

Sreekala-Gopakumar · 2025-03-25T13:05:23Z

@h3110n3rv3 @pshipton - I have updated the topics. Please check and confirm that the information is correct. Could you please especially check the following:

examples given in https://eclipse-openj9.github.io/openj9-docs-staging/1497/xtrace/#maxstringlength

whether the new option is placed under the correct section i.e. https://eclipse-openj9.github.io/openj9-docs-staging/1497/xtrace/#configuring-trace

Can this be added as a new feature in the 0.50.0 release section - https://eclipse-openj9.github.io/openj9-docs-staging/1497/version0.50/ ?

Thanks!

@h3110n3rv3 - Could you please review and let me know if any changes are required. Thanks!

h3110n3rv3 · 2025-03-27T16:09:23Z

@Sreekala-Gopakumar Sorry if I wasn't clear in my previous comment.
The default now is address + 32 characters of string (i.e., if maxstringlength is not provided) - before this feature, it used to be only address printing with no way to print actual strings. This only affects tracing where addresses were printed for string arguments/return values.
maxstringlength provides a way for printing custom length of string arguments/return values.
examples:
Default behavior now:
-Xtrace:methods={java/lang/String.concat'()'},print=mt --> address + 32 string characters
12:31:00.323 0x25a00 mt.18 - this: java/lang/String@00000006049B84B8 method arguments: ((String)"Lorem ipsum dolor sit amet, cons"...)
12:31:00.323 0x25a00 mt.28 - return value: java/lang/String@00000007FFF92A80 - (String)"HelloLorem ipsum dolor sit amet,"...

maxstringlength set to 0:
-Xtrace:methods={java/lang/String.concat'()'},print=mt,maxstringlength=0 --> address only
12:35:58.213 0x25a00 mt.18 - this: java/lang/String@00000006049B84B8 method arguments: (java/lang/String@00000006049B84E0)
12:35:58.213 0x25a00 mt.28 - return value: java/lang/String@00000007FFF92AD8

maxstringlength set to custom value (max 128):
-Xtrace:methods={java/lang/String.concat'()'},print=mt,maxstringlength=80 --> prints address + 80 string characters
12:37:52.935 0x25a00 mt.18 - this: java/lang/String@00000006049B84B8 method arguments: ((String)"Lorem ipsum dolor sit amet, consectetuer adipiscing elit. Aenean commodo ligula "...)
12:37:52.935 0x25a00 mt.28 - return value: java/lang/String@00000007FFF92AE0 - (String)"HelloLorem ipsum dolor sit amet, consectetuer adipiscing elit. Aenean commodo li"...

Sreekala-Gopakumar · 2025-03-27T17:48:55Z

Jenkins doc stage

Sreekala-Gopakumar · 2025-03-27T17:54:52Z

@h3110n3rv3 @pshipton - I have made the changes. Please check and let me know if any further changes are required. Thanks!

h3110n3rv3 · 2025-03-27T18:46:37Z

@Sreekala-Gopakumar Most of it looks good.
Just a minor suggestion: I think we should specify that maxstringlength is to print string argument/return values of custom length since, now, by default string+addresses are printed.
You can use the maxstringlength parameter of the -Xtrace option to specify the custom length of string arguments being passed, as well as the values returned from the methods, to be printed along with the addresses in a trace output.

Sreekala-Gopakumar · 2025-03-28T05:49:13Z

Jenkins doc stage

Sreekala-Gopakumar · 2025-03-28T06:04:00Z

Jenkins doc stage

Sreekala-Gopakumar · 2025-03-28T06:15:43Z

@h3110n3rv3 @pshipton - Please check and confirm. Thanks!

h3110n3rv3 · 2025-03-24T12:43:34Z

docs/xtrace.md

+Use to print the string arguments sent to and the values that are returned from the methods as strings instead of addresses in a trace output. The range of the maximum string length that can be set is 0-128. If the length is not specified, 32 characters of the strings are printed by default. If `maxstringlength=0`, the string addresses are printed instead.
+
+This parameter is used with other method tracing options, such as `-Xtrace:methods={java/lang/String.concat'()'}`. While using such method tracing options, the argument is passed to this function as a string and the value is returned as a string. Without this parameter, you cannot capture the contents of the string arguments and return values. Only the address of the string object is displayed. If you want to see the string that is passed to and returned from a method for debugging purposes, use the `maxstringlength` parameter.
+


@Sreekala-Gopakumar Sorry if I wasn't clear in my previous comment.
The default now is address + 32 characters of string (i.e., if maxstringlength is not provided) - before this feature, it used to be only address printing with no way to print actual strings. This only affects tracing where addresses were printed for string arguments/return values.
maxstringlength provides a way for printing custom length of string arguments/return values.
examples:
Default behavior now:
-Xtrace:methods={java/lang/String.concat'()'},print=mt --> address + 32 string characters
12:31:00.323 0x25a00 mt.18 - this: java/lang/String@00000006049B84B8 method arguments: ((String)"Lorem ipsum dolor sit amet, cons"...)
12:31:00.323 0x25a00 mt.28 - return value: java/lang/String@00000007FFF92A80 - (String)"HelloLorem ipsum dolor sit amet,"...

maxstringlength set to 0:
-Xtrace:methods={java/lang/String.concat'()'},print=mt,maxstringlength=0 --> address only
12:35:58.213 0x25a00 mt.18 - this: java/lang/String@00000006049B84B8 method arguments: (java/lang/String@00000006049B84E0)
12:35:58.213 0x25a00 mt.28 - return value: java/lang/String@00000007FFF92AD8

maxstringlength set to custom value (max 128):
-Xtrace:methods={java/lang/String.concat'()'},print=mt,maxstringlength=80 --> prints address + 80 string characters
12:37:52.935 0x25a00 mt.18 - this: java/lang/String@00000006049B84B8 method arguments: ((String)"Lorem ipsum dolor sit amet, consectetuer adipiscing elit. Aenean commodo ligula "...)
12:37:52.935 0x25a00 mt.28 - return value: java/lang/String@00000007FFF92AE0 - (String)"HelloLorem ipsum dolor sit amet, consectetuer adipiscing elit. Aenean commodo li"...

@Sreekala-Gopakumar

Sreekala-Gopakumar · 2025-04-01T02:52:01Z

@pshipton - Can this be merged? Thanks!

pshipton · 2025-04-01T12:20:50Z

docs/xtrace.md

-| [`-Xtrace:trigger=<clause>`](#trigger)                             | Determines when various triggered trace actions occur, including turning trace on or off.          |
+| [`-Xtrace:buffers=<size>[dynamic\|nodynamic]`](#buffers)           | Modifies the size of buffers that are used to store trace data                      |
+| [`-Xtrace:exception.output=<filename>[,<size>]`](#exceptionoutput) | Redirects exceptions trace data to a file                                           |
+| [`-Xtrace:maxstringlength=[<length>]`](#maxstringlength)           | Specifies the length of the string arguments and the values of the methods that are printed in addition to the string object addresses in a trace output               |


return values

pshipton · 2025-04-01T12:25:01Z

docs/xtrace.md

+
+Use to specify the length of the string arguments and return values that are printed in a trace output. The range of the maximum string length that can be set is 0-128. If the length is not specified, 32 characters of the strings are printed by default along with the addresses. If `maxstringlength=0`, only the string addresses are printed instead.
+
+This parameter is used with other method tracing options, such as `-Xtrace:methods={java/lang/String.concat'()'}` and affects only those tracing operations where addresses are printed for string arguments and return values. When using such method tracing options, the argument is passed to the function as a string and the value is returned as a string. Earlier, you could not capture the contents of the string arguments and return values. Only the address of the string object was printed. Now, both the actual strings as well as the addresses can be printed.


should it be "and return values, only the address" using a comma instead of period?

eclipse-openj9#1466 Added the new parameter, `maxstringlength`. Incorporated review feedback. Closes eclipse-openj9#1466 Signed-off-by: Sreekala Gopakumar sreekala.gopakumar@ibm.com

Sreekala-Gopakumar · 2025-04-01T16:17:12Z

Jenkins doc stage

Sreekala-Gopakumar · 2025-04-01T16:32:44Z

@pshipton - Incorporated the suggested changes. Thanks!

Sreekala-Gopakumar force-pushed the 1466XtraceMaxStr branch from ec7a2bf to 6525061 Compare March 20, 2025 18:59

Sreekala-Gopakumar self-assigned this Mar 20, 2025

Sreekala-Gopakumar added this to the Release 0.50 (Java24 GA) milestone Mar 20, 2025

Sreekala-Gopakumar force-pushed the 1466XtraceMaxStr branch 2 times, most recently from 186ef85 to 9dbfac9 Compare March 27, 2025 17:48

Sreekala-Gopakumar force-pushed the 1466XtraceMaxStr branch from 9dbfac9 to 3d5fc4f Compare March 28, 2025 05:48

Sreekala-Gopakumar force-pushed the 1466XtraceMaxStr branch from 3d5fc4f to fe56f5c Compare March 28, 2025 06:03

h3110n3rv3 approved these changes Mar 31, 2025

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pshipton reviewed Apr 1, 2025

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Add documentation for -Xtrace:maxstringlength option

9b08104

eclipse-openj9#1466 Added the new parameter, `maxstringlength`. Incorporated review feedback. Closes eclipse-openj9#1466 Signed-off-by: Sreekala Gopakumar sreekala.gopakumar@ibm.com

Sreekala-Gopakumar force-pushed the 1466XtraceMaxStr branch from fe56f5c to 9b08104 Compare April 1, 2025 16:15

pshipton approved these changes Apr 1, 2025

View reviewed changes

pshipton merged commit c97dfda into eclipse-openj9:master Apr 1, 2025
3 checks passed

		Use to print the string arguments sent to and the values that are returned from the methods as strings instead of addresses in a trace output. The range of the maximum string length that can be set is 0-128. If the length is not specified, 32 characters of the strings are printed by default. If `maxstringlength=0`, the string addresses are printed instead.

		This parameter is used with other method tracing options, such as `-Xtrace:methods={java/lang/String.concat'()'}`. While using such method tracing options, the argument is passed to this function as a string and the value is returned as a string. Without this parameter, you cannot capture the contents of the string arguments and return values. Only the address of the string object is displayed. If you want to see the string that is passed to and returned from a method for debugging purposes, use the `maxstringlength` parameter.


		Use to specify the length of the string arguments and return values that are printed in a trace output. The range of the maximum string length that can be set is 0-128. If the length is not specified, 32 characters of the strings are printed by default along with the addresses. If `maxstringlength=0`, only the string addresses are printed instead.

		This parameter is used with other method tracing options, such as `-Xtrace:methods={java/lang/String.concat'()'}` and affects only those tracing operations where addresses are printed for string arguments and return values. When using such method tracing options, the argument is passed to the function as a string and the value is returned as a string. Earlier, you could not capture the contents of the string arguments and return values. Only the address of the string object was printed. Now, both the actual strings as well as the addresses can be printed.

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