[Mono-bugs] [Bug 79106][Nor] Changed - Default-constructed StringBuilder unusable with P/Invoke

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Changed by jonpryor at vt.edu.

http://bugzilla.ximian.com/show_bug.cgi?id=79106

--- shadow/79106	2006-08-18 19:44:41.000000000 -0400
+++ shadow/79106.tmp.9292	2006-08-20 19:56:32.000000000 -0400
@@ -1,23 +1,23 @@
 Bug#: 79106
 Product: Mono: Class Libraries
 Version: 1.1
-OS: 
+OS: unknown
 OS Details: Ubuntu 6.06; mono 1.1.13.6
 Status: NEW   
 Resolution: 
-Severity: 
+Severity: Unknown
 Priority: Normal
-Component: Mono.POSIX
+Component: CORLIB
 AssignedTo: miguel at ximian.com                            
 ReportedBy: Ziktar at DeadMoose.com               
 QAContact: mono-bugs at ximian.com
 TargetMilestone: ---
 URL: 
 Cc: 
-Summary: Mono.Unix.Native.Syscall.readlink crashes when passed empty StringBuilder
+Summary: Default-constructed StringBuilder unusable with P/Invoke
 
 Description of Problem:
 
 Calling Mono.Unix.Native.Syscall.readlink with an empty StringBuilder will
 crash (not throw an exception, but SIGSEGV).
 
@@ -61,6 +61,23 @@
 
 Every time.
 
 Additional Information:
 
 Note that calling this with a "new StringBuffer(x);" where x >= 0 will work.
+
+------- Additional Comments From jonpryor at vt.edu  2006-08-20 19:56 -------
+This appears to be a bug within System.Text.StringBuilder, where use
+of the default constructor sets StringBuilder._str to "", while
+StringBuilder((int)0) sets StringBuilder._str to a string of length
+StringBuilder.constDefaultCapacity.
+
+Result: use of the default constructor yields an unusable
+StringBuilder isntance (as far as P/Invoke is concerned).
+
+(Note: There is nothing that Mono.Unix.Native.Syscall.readlink() could
+do to check this, since the default-constructed StringBuilder returns
+a .Capacity of 16, so there's no way I know of to distinguish between
+a default-constructed and a non-default-constructed StringBuilder
+instance.)
+
+--> System.Text.StringBuilder bug.