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POANTLR StringTemplate infinite loop while rendering the template
 

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  1. POANTLR StringTemplate infinite loop while rendering the template
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    <p>I am using antlr-3.4-complete.jar which i believe is using StringTemplate version 3.2.1</p> <p>I have the following productions in the tree grammar</p> <pre><code>functionCall : ^(FUNCCALL NCName pr+=params*) -&gt;template(n={$NCName.text},p={$pr})"&lt;n&gt; &lt;p&gt;" </code></pre> <p>The above StringTemplate runs correctly and is generating correct output.</p> <p>I have another production in the same grammar which is very similar to the production above</p> <pre><code>step : axisSpecifier nodeTest pred+=predicate* -&gt;template(a={$axisSpecifier.st},n={$nodeTest.st},pc={$pred})"&lt;a&gt; &lt;n&gt; &lt;pc&gt;" ; </code></pre> <p>But when i print the template it goes in infinite recursion, the stack is as below</p> <pre><code>Exception in thread "main" java.lang.StackOverflowError at org.antlr.stringtemplate.StringTemplate.getAttributeRenderer(StringTemplate.java:1080) at org.antlr.stringtemplate.StringTemplate.getAttributeRenderer(StringTemplate.java:1080) at org.antlr.stringtemplate.StringTemplate.getAttributeRenderer(StringTemplate.java:1080) at org.antlr.stringtemplate.StringTemplate.getAttributeRenderer(StringTemplate.java:1080) at org.antlr.stringtemplate.StringTemplate.getAttributeRenderer(StringTemplate.java:1080) at org.antlr.stringtemplate.StringTemplate.getAttributeRenderer(StringTemplate.java:1080) at org.antlr.stringtemplate.StringTemplate.getAttributeRenderer(StringTemplate.java:1080) at org.antlr.stringtemplate.StringTemplate.getAttributeRenderer(StringTemplate.java:1080) at org.antlr.stringtemplate.StringTemplate.getAttributeRenderer(StringTemplate.java:1080) at org.antlr.stringtemplate.StringTemplate.getAttributeRenderer(StringTemplate.java:1080) at org.antlr.stringtemplate.StringTemplate.getAttributeRenderer(StringTemplate.java:1080) at org.antlr.stringtemplate.StringTemplate.getAttributeRenderer(StringTemplate.java:1080) at org.antlr.stringtemplate.StringTemplate.getAttributeRenderer(StringTemplate.java:1080) at org.antlr.stringtemplate.StringTemplate.getAttributeRenderer(StringTemplate.java:1080) at org.antlr.stringtemplate.StringTemplate.getAttributeRenderer(StringTemplate.java:1080) </code></pre> <p>The generated code for the above production is as below</p> <pre><code>retval.st = new StringTemplate(templateLib, "&lt;a&gt; &lt;n&gt; &lt;pc&gt;",new STAttrMap().put("a", (axisSpecifier14!=null?axisSpecifier14.st:null)).put("n", (nodeTest15!=null?nodeTest15.st:null)).put("pc", list_pred)); </code></pre> <p>The <code>list_pred</code> is the list containing the StringTemplates for <code>predicate*</code>. When i debug the code i find that just before the above line, the individual StringTemplates are fine. By being fine i mean i can read the value in the debugger as the String value. But as soon as the above line is executed, i.e. <code>new StringTemplate</code> is done, the <code>toString()</code> method starts to fail. not only for the new StringTemplate but also for the StringTemplate <code>list_pred</code></p> <p>I am unable to go forward with my work, as i dont think this is a problem with my grammar, as another production with same structure is working fine.</p> <p>Can this error occur because of the parameter names i have chosen? </p> <p><code>template(a={$axisSpecifier.st},n={$nodeTest.st},pc={$pred})"&lt;a&gt; &lt;n&gt; &lt;pc&gt;"</code></p> <p>if i change the names from <code>a</code>,<code>n</code>,<code>pc</code> to something else will it help? as i see i have used the same names other places in the grammar also.</p> <p>I suspect the method</p> <p><code>StringTemplate.breakTemplateIntoChunks()</code> might be the reason here? as this method will parse the template.</p> <p>Can someone familiar with StringTemplate internals help me with this issue?</p> <p>Thanks, Regards, Vimal</p> <p><strong>UPDATE:</strong> This is the output from my AST construction, this also forms the input for treeGrammar. <code>(VARREF abc) / (STEPS (STEP child x (PRED (&lt; (STEPS (STEP child price)) 10)))) END</code> </p> <p>The <code>PRED</code> is the predicate which is also an <code>Expr</code></p> <p>My Tree Grammars with ST is as follows.</p> <pre><code>expr : ^('&lt;' e1=expr e2=expr) -&gt;template(e11={$e1.st},e21={$e2.st})"\&lt; &lt;e11&gt; &lt;e21&gt;" | mainexpr -&gt; template(mnexpr={$mainexpr.st})"&lt;mnexpr&gt;" ; mainexpr scope { boolean isRLP ; } : filterExpr ('/' {$mainexpr::isRLP = true;} relativeLocationPath)? -&gt; {$mainexpr::isRLP}? template(filtr={$filterExpr.st},rlp= {$relativeLocationPath.st})"&lt;filtr&gt; &lt;rlp&gt;" -&gt; template(filtr={$filterExpr.st})"&lt;filtr&gt;" | relativeLocationPath -&gt; template(rlp={$relativeLocationPath.st})"&lt;rlp&gt;" ; relativeLocationPath : ^(STEPS st+=steps+) -&gt; template(stps={$st})"&lt;stps&gt;"; steps : ^(STEP step) -&gt;template(stp={$step.st})"&lt;stp&gt;" ; step : axisSpecifier nodeTest (pred+=predicate)* -&gt;template(axs={$axisSpecifier.st},ndtst={$nodeTest.st},stppred={$pred})"&lt;axs&gt; &lt;ndtst&gt; &lt;stppred&gt;" ; predicate : ^(PRED expr) -&gt;template(predexp={$expr.st})"&lt;predexp&gt;" ; </code></pre> <p>Output of LintMode:</p> <pre><code>Exception in thread "main" java.lang.IllegalStateException: infinite recursion to &lt;anonymous([])@76&gt; referenced in &lt;anonymous([])@69&gt;; stack trace: &lt;anonymous([])@76&gt;, attributes=[predexp=&lt;anonymous()@75&gt;], references=[predexp, stppred]&gt; &lt;anonymous([])@69&gt;, attributes=[ndtst=&lt;anonymous()@68&gt;, stppred, axs=&lt;anonymous()@67&gt;], references=[axs, ndtst, stppred]&gt; &lt;anonymous([])@70&gt;, attributes=[stp=&lt;anonymous()@69&gt;], references=[stp, stppred]&gt; &lt;anonymous([])@71&gt;, attributes=[stps=List[..&lt;anonymous()@70&gt;..]], references=[stps, stppred]&gt; &lt;anonymous([])@72&gt;, attributes=[rlp=&lt;anonymous()@71&gt;], references=[rlp, stppred]&gt; &lt;anonymous([])@73&gt;, attributes=[mnexpr=&lt;anonymous()@72&gt;], references=[mnexpr, stppred]&gt; &lt;anonymous([])@75&gt;, attributes=[e21=&lt;anonymous()@74&gt;, e11=&lt;anonymous()@73&gt;], references=[e11, stppred]&gt; &lt;anonymous([])@76&gt; (start of recursive cycle) </code></pre>
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    1. CODoesn't ANTLR 3.4 use StringTemplate v4? You might want to ask your question on the [StringTemplate mailing-list](http://www.antlr.org/mailman/listinfo/stringtemplate-interest): Terence roams SO from time to time, but there aren't a lot of *StringTemplaters* around here (yet!) :) Good luck!
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      1. USBart Kiers
    2. CO@BartKiers, thansk for your response. I print the value of variable `StringTemplate.VERSION` and i get 3.2.1 so i say it uses 3.2.1. Also the source i downloaded for 3.2.1 is able to match with code when i debug.
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      1. USweima
    3. CO@BartKiers the problem is somewhere in StringTemplate.toString() and the trouble with debugging this method is that when i am trying to locate the source of error, whenever i check the value of any StringTemplate, the debugger internally calls the `toString()` before i can complete my stepping of toString() :)
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