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851cd03941
program and libraries are named ecl*. Finally the routine sys::build-ecls has been renamed sys::build-program.
89 lines
2 KiB
Text
89 lines
2 KiB
Text
THINGS IN THIS FILE
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===================
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This file documents assumptions which are made throughout the ECLS code. Most
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of them are critical and a lot of code relies on them, some others are very
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localized but in critical points (eval, apply, etc). In general great care
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must be taken so that changes in ECLS do not break these "invariants".
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REAL BUGS
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=========
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* Routines in bind.c do not check length of arguments and may cause buffer
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overflows.
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* The following routines may cause indefinite loops when passed circular
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lists:
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GCC SPECIFICS
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=============
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* Stack allocatable arrays of variable size, i.e.,
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int function(int size) {
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object x[size];
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...
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* Functions with a variable number of arguments are called with the
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same protocol as ordinary functions, i.e., the following code is
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valid
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#in "foo.c"
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extern int fa(int foo, ...);
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int test(object x) {
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faa(1, x);
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}
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#in "faa.c"
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int faa(int foo, object x) {
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...
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}
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* Arguments of any function can be acessed as elements of an array.
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#in "foo.c"
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int test(object *x) {
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...
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}
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#in "faa.c"
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int faa(int foo, object x, ...) {
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test(&x);
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}
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OPERATING SYSTEM
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================
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* Stack checks are required in compiled code to make sure recursion
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does not get too deep. This makes sense in multithreaded code, but
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do unix-like operating systems really provide no stack protection?
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ECLS CODE INVARIANTS
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====================
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* C structs are aligned at least at 4 bytes, so that Cnil is a valid
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object pointer.
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* "struct symbol" and "struct cons" share fields so that
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Cnil->c.c_car == Cnil->c.c_cdr == Cnil.
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* "struct array", "struct vector", "struct string, "struct bitvector"
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share a number of fields, such as "*_dim", "*_self", etc.
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* Boehm's garbage collector returns pointers with two lower bits set
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to zero, i.e.,
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((int)GC_malloc(n)) & 3 == 0
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* Frame/binding/history stacks cannot be resized.
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* DATA_START % LISP_PAGESIZE == 0
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;;; Local Variables: ***
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;;; mode:text ***
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;;; fill-column:79 ***
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;;; End: ***
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