[fpc-pascal] Re: Stack checking in dynamic libraries
cobines
cobines at gmail.com
Sun Nov 8 18:22:38 CET 2009
A followup from the previous mail. I have expanded the program to
query pthreads library directly for thread's stack info. Here are the
results (the lines containing "Pthr" string have values reported by
the pthreads library):
MainThreadId : 3076675264
< main thread, main program >
CurrentThreadId : 3076675264
Thread ID : 3078065408
Stack ptr : BFC4B964
Stack top : 00000000
Stack bottom : BF44BA8C
Stack length : 8388608
Pthr ThreadId : 3076675264
Pthr Stack ptr : BFC4B928
Pthr Stack top : BFC4D000
Pthr Stack bot : BF44D000
Pthr Stack Len : 8388608
< main thread, library >
Libr. CurrentThreadId: 3076675264
Libr. ThreadId : 3078065408
Libr. Stack ptr : BFC4B964
Libr. Stack top : 00000000
Libr. Stack bottom : BF44B694
Libr. Stack length : 8388608
Libr. Pthr ThreadId : 3076675264
Libr. Pthr Stack ptr : BFC4B928
Libr. Pthr Stack top : BFC4D000
Libr. Pthr Stack bot : BF44D000
Libr. Pthr Stack Len : 8388608
< worker thread, main program >
CurrentThreadId : 3075664752
Thread ID : 3075664752
Stack ptr : B752E17C
Stack top : 00000000
Stack bottom : B712E300
Stack length : 4194304
Pthr ThreadId : 3075664752
Pthr Stack ptr : B752E140
Pthr Stack top : B752F000
Pthr Stack bot : B712E000
Pthr Stack Len : 4198400
< worker thread, library >
Libr. CurrentThreadId: 3075664752
Libr. ThreadId : 3078065408
Libr. Stack ptr : B752E17C
Libr. Stack top : 00000000
Libr. Stack bottom : BF44B694
Libr. Stack length : 8388608
Libr. Pthr ThreadId : 3075664752
Libr. Pthr Stack ptr : B752E140
Libr. Pthr Stack top : B752F000
Libr. Pthr Stack bot : B712E000
Libr. Pthr Stack Len : 4198400
The values for < worker thread, library > reported by pthreads appear
to be correct.
First, the stack size is ~ 4MB, which is the worker thread's stack
size, although I'm don't know why the discrepancy: 4194304 vs 4198400
bytes.
Second, the stack address begins with B7.... (address of the main
thread's stack begins with BF.....).
Third, the stack pointer is well within the stack limits: B712E000 <
B752E140 < B752F000.
I have to conclude that the values in rtl/inc/systemh.inc: StackTop,
StackBottom, StackLength are not behaving as thread-specific variables
in the library, even though they are declared using ThreadVar. The
IsMultiThread value in < worker thread, main program > is TRUE, but in
< worker thread, library > it is FALSE. Do I have to initialize
multithreading in the dynamic library somehow?
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