Author: Gerd Isenberg
Date: 06:53:51 10/25/05
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On October 25, 2005 at 08:39:07, Daniel Mehrmannn wrote: >Hi, > >well i found a bug in my engine. I declare the boolean variable "stop_search" in >search.c. I made the error that i call this variable as "extern int stop_search" >from other files. > >Interesting: >- No compiler found this error (gcc, icc, vc 6.0 (also solaris)) >- On Windows and Linux(!) the engine runs without any problems. > >Expect Solaris 8-10 (Sparc) family created a "segmentation fault" at first >access. > >How is this possible ? Why other plattforms and compiler ignored this problem ? >I only do a read access of this extern variable. > >see here: http://www.homer-chess.com/images/sol9.jpg > >Best, >Daniel Hi Daniel, it depends where the linker "allocates" the boolean variable with sizeof one byte. If it is "near" a 4K-Page boundary (1000h), let say at 0xffe or 0xfff, a byte read/write is fine, while an "external" dword read will crash. Did you do the external declaration inside a shared header file (i guess no)? Imagine the extern declaration is included from a shared h file, extern int foo; bool foo; then the compiler recognizes the error: error C2371: 'foo' : redefinition; different basic types while this is fine: extern bool foo; bool foo; Otherwise with disjoint declaration in C-files the compiler has no chance to detect the error, while the linker is probably overstrained with type checking of symbols (probably one reason that C++ names put some type information to symbols). Gerd
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