Add more bugs & quirks

SourceGen/RuntimeData/Help/codegen.html

@@ -166,6 +166,7 @@ code, but also needs to know how to handle the corner cases.</p>
   <li>PC relative branches don't wrap around at bank boundaries.</li>
   <li>BRK &lt;arg&gt; is assembled to opcode $05 rather than $00.</li>
   <li>WDM is not supported.</li>
+  <li>Source file names must not have spaces in them on Windows.</li>
 </ul>
 
 <p>Quirks:</p>
@@ -179,6 +180,11 @@ code, but also needs to know how to handle the corner cases.</p>
     SourceGen currently generates require parenthesis.)</li>
   <li>Undocumented opcodes: SBX ($cb) uses the mnemonic AXS.  All other
     opcodes match up with the "unintended opcodes" document.</li>
+  <li>ca65 is implemented as a single-pass assembler, so label widths
+    can't always be known in time.  For example, if you .ORG $0000 after
+    the point where the labels are used, the assembler will already have
+    generated them as absolute values.  Width disambiguation must be applied
+    to instructions that aren't ambiguous to multi-pass assemblers.</li>
 </ul>
 
 
@@ -190,6 +196,8 @@ code, but also needs to know how to handle the corner cases.</p>
 <ul>
   <li>PC relative branches don't wrap around at bank boundaries.</li>
   <li>For some failures, an exit code of zero is returned.</li>
+  <li>Some indexed store instructions cause errors if the label isn't
+    unambiguously DP (e.g. `STX $00,X` vs. `STX $0000,X`).</li>
 </ul>
 
 <p>Quirks:</p>

SourceGen/RuntimeData/Help/editors.html

@@ -39,8 +39,10 @@ is set to 65816.</p>
 
 <h2><a name="label">Edit Label</a></h2>
 <p>Sets or clears a label at the selected offset.  The label must have
-the proper form, and not have the same name as another symbol.  If
+the
-you edit an auto-generated label you will be required to change the name.</p>
+<a href="intro.html#about-symbols">proper form</a>, and not have the same
+name as another symbol.  If you edit an auto-generated label you will
+be required to change the name.</p>
 <p>The label may be marked as local, global, or global and exported.
 Local labels may be modified by the assembly code generator to have a more
 convenient form, such as a local loop identifier.  Global labels are

SourceGen/RuntimeData/Help/intro.html

@@ -378,6 +378,11 @@ with most assemblers:</p>
 </ul>
 <p>Label comparisons are case-sensitive, as is customary for programming
 languages.</p>
+<p>Some assemblers restrict the set of valid labels further.  For example,
+64tass uses a leading underscore to indicate a local label, and reserves
+a double leading underscore (e.g. <code>__label</code>) for its own
+purposes.  In such cases, the label will be modified to comply with the
+target assembler syntax.</p>
 
 <p><b>Platform symbols</b> are defined in platform symbol files.  These
 are named with a ".sym65" extension, and have a fairly straightforward