CallStack (System function): Difference between revisions
Jump to navigation
Jump to search
mNo edit summary |
m (→Usage Notes) |
||
| (25 intermediate revisions by 5 users not shown) | |||
| Line 1: | Line 1: | ||
< | {{Template:System:CallStack subtitle}} | ||
[[ | The <var>CallStack</var> shared function returns a <var>[[Stringlist_class|Stringlist]]</var> containing information about the current call stack: information about the caller of the current method or subroutine, the caller of that caller, and so on. | ||
< | ==Syntax== | ||
{{Template:System:CallStack syntax}} | |||
===Syntax terms=== | |||
<table class="syntaxTable"> | |||
<tr><th>%sl</th><td>A <var>Stringlist</var> object to be set to reference the object that contains information about the current call stack. The first item in the <var>Stringlist</var> refers to the immediate caller of the current method or subroutine; a second item refers to the caller of that caller, if any; and so on.</td></tr> | |||
<tr><th><var class="nobr">%(System)</var></th><td>The class name in parentheses denotes a [[Notation conventions for methods#Shared methods|shared]] method.</td></tr> | |||
</table> | |||
==Usage Notes== | |||
<ul> | |||
<li><var>CallStack</var> returns the name of the procedure and the line within the procedure that made the calls of the current method or subroutine. Generally, each returned <var>Stringlist</var> item has the name of the file containing the calling procedure at positions one through eight, followed by a blank, followed by the name of the calling procedure, followed by a blank, followed by the line number within the calling procedure. | |||
<p class="note"><b>Note:</b> The call stack information returned by <var>CallStack</var> refers to the (names of and line numbers in) procedures that contain the calls to the current method or subroutine, ''not'' to (names of and line numbers in) the current subroutine or method.</p></li> | |||
<li>For method or subroutine calls that were entered at command level (not inside a procedure), the <var class="term">%sl</var> item will contain a single asterisk character (<tt>*</tt>). | |||
If <var>CallStack</var> cannot determine the location of the call, the <var class="term">%sl</var> item associated with a call will be null (zero-length). If not issued from within a method or subroutine, <var>CallStack</var> will return an empty (zero-item) Stringlist.</li> | |||
<li>For <var>CallStack</var> to determine the location of a method or subroutine call, source line information must be collected at compile time. Either you must set the <var>[[SIRFACT_parameter|SIRFACT]]</var> system parameter's X'01' bit, or the request must be compiled with the <var class="product">Model 204</var> <var>DEBUGUL</var> user parameter set to a non-zero value. | |||
<p> | <p> | ||
CallStack is a | To use the <var>SIRFACT</var> system parameter, your site must be authorized for <var class="product">[[SirFact]]</var>. Using the <var>DEBUGUL</var> user parameter increases the <var>QTBL</var> and (to a lesser degree) <var>VTBL</var> requirements for a compiled request.</p></li> | ||
<li>The <var>CallStack</var> method is intended to be used for problem diagnosis and, perhaps, for logging and auditing. Using it to affect method or subroutine behavior by causing a method or subroutine to behave differently depending on its caller is <b><i>extremely</i></b> poor technique, and it cannot be discouraged strongly enough. </li> | |||
</ul> | |||
==Examples== | |||
In the MYTAX.UL procedure, the computeTax1 subroutine is called by the computeTax2 subroutine at line 146. If you issue the following statements from within computeTax1: | |||
<p class="code">%callList is object stringlist | |||
%callList = %(system):callStack | |||
%callList:[[Print_(Stringlist_function)|print]] | |||
</p> | </p> | ||
The result is something like the following: | The result is something like the following: | ||
<p class=" | <p class="output">MYPROC MYTAX.UL 193 | ||
MYPROC MYTAX.UL 146 | MYPROC MYTAX.UL 146 | ||
</p> | |||
==See Also== | |||
{{Template:System:CallStack footer}} | |||
Latest revision as of 19:45, 2 July 2014
Current call stack description (System class)
The CallStack shared function returns a Stringlist containing information about the current call stack: information about the caller of the current method or subroutine, the caller of that caller, and so on.
Syntax
%sl = %(System):CallStack
Syntax terms
| %sl | A Stringlist object to be set to reference the object that contains information about the current call stack. The first item in the Stringlist refers to the immediate caller of the current method or subroutine; a second item refers to the caller of that caller, if any; and so on. |
|---|---|
| %(System) | The class name in parentheses denotes a shared method. |
Usage Notes
- CallStack returns the name of the procedure and the line within the procedure that made the calls of the current method or subroutine. Generally, each returned Stringlist item has the name of the file containing the calling procedure at positions one through eight, followed by a blank, followed by the name of the calling procedure, followed by a blank, followed by the line number within the calling procedure.
Note: The call stack information returned by CallStack refers to the (names of and line numbers in) procedures that contain the calls to the current method or subroutine, not to (names of and line numbers in) the current subroutine or method.
- For method or subroutine calls that were entered at command level (not inside a procedure), the %sl item will contain a single asterisk character (*). If CallStack cannot determine the location of the call, the %sl item associated with a call will be null (zero-length). If not issued from within a method or subroutine, CallStack will return an empty (zero-item) Stringlist.
- For CallStack to determine the location of a method or subroutine call, source line information must be collected at compile time. Either you must set the SIRFACT system parameter's X'01' bit, or the request must be compiled with the Model 204 DEBUGUL user parameter set to a non-zero value.
To use the SIRFACT system parameter, your site must be authorized for SirFact. Using the DEBUGUL user parameter increases the QTBL and (to a lesser degree) VTBL requirements for a compiled request.
- The CallStack method is intended to be used for problem diagnosis and, perhaps, for logging and auditing. Using it to affect method or subroutine behavior by causing a method or subroutine to behave differently depending on its caller is extremely poor technique, and it cannot be discouraged strongly enough.
Examples
In the MYTAX.UL procedure, the computeTax1 subroutine is called by the computeTax2 subroutine at line 146. If you issue the following statements from within computeTax1:
%callList is object stringlist %callList = %(system):callStack %callList:print
The result is something like the following:
MYPROC MYTAX.UL 193 MYPROC MYTAX.UL 146