Describe quoting rules.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@36060 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 46 insertions, 4 deletions

diff --git a/docs/TestingGuide.html b/docs/TestingGuide.html
index df8cfefddf..f03adaaef6 100644
--- a/docs/TestingGuide.html
+++ b/docs/TestingGuide.html
@@ -323,6 +323,13 @@ location of these external programs is configured by the llvm-test
   any process in the pipeline fails, the entire line (and test case) fails too.
   </p>
 
+  <p> Below is an example of legal RUN lines in a <tt>.ll</tt> file:</p>
+  <pre>
+  ; RUN: llvm-as &lt; %s | llvm-dis &gt; %t1
+  ; RUN: llvm-dis &lt; %s.bc-13 &gt; %t2
+  ; RUN: diff %t1 %t2
+  </pre>
+
   <p>As with a Unix shell, the RUN: lines permit pipelines and I/O redirection
   to be used. However, the usage is slightly different than for Bash. To check
   what's legal, see the documentation for the 
@@ -341,12 +348,47 @@ location of these external programs is configured by the llvm-test
     shouldn't use that here.</li>
   </ul>
 
-  <p> Below is an example of legal RUN lines in a <tt>.ll</tt> file:</p>
+  <p>There are some quoting rules that you must pay attention to when writing
+  your RUN lines. In general nothing needs to be quoted. Tcl won't strip off any
+  ' or " so they will get passed to the invoked program. For example:</p>
   <pre>
-  ; RUN: llvm-as &lt; %s | llvm-dis &gt; %t1
-  ; RUN: llvm-dis &lt; %s.bc-13 &gt; %t2
-  ; RUN: diff %t1 %t2
+     ... | grep 'find this string'
   </pre>
+  <p>This will fail because the ' characters are passed to grep. This would
+  instruction grep to look for <tt>'find</tt> in the files <tt>this</tt> and
+  <tt>string'</tt>. To avoid this use curly braces to tell Tcl that it should
+  treat everything enclosed as one value. So our example would become:</p>
+  <pre>
+     ... | grep {find this string}
+  </pre>
+  <p>Additionally, the characters <tt>[</tt> and <tt>]</tt> are treated 
+  specially by Tcl. They tell Tcl to interpret the content as a command to
+  execute. Since these characters are often used in regular expressions this can
+  have disastrous results and cause the entire test run in a directory to fail.
+  For example, a common idiom is to look for some basicblock number:</p>
+  <pre>
+     ... | grep bb[2-8]
+  </pre>
+  <p>This, however, will cause Tcl to fail because its going to try to execute
+  a program named "2-8". Instead, what you want is this:</p>
+  <pre>
+     ... | grep {bb\[2-8\]}
+  </pre>
+  <p>Finally, if you need to pass the <tt>\</tt> character down to a program,
+  then it must be doubled. This is another Tcl special character. So, suppose
+  you had:
+  <pre>
+     ... | grep 'i32\*'
+  </pre>
+  <p>This will fail to match what you want (a pointer to i32). First, the
+  <tt>'</tt> do not get stripped off. Second, the <tt>\</tt> gets stripped off
+  by Tcl so what grep sees is: <tt>'i32*'</tt>. That's not likely to match
+  anything. To resolve this you must use <tt>\\</tt> and the <tt>{}</tt>, like
+  this:</p>
+  <pre>
+     ... | grep {i32\\*}
+  </pre>
+
 </div>
 
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