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-rw-r--r--fitz/fitz.h128
1 files changed, 0 insertions, 128 deletions
diff --git a/fitz/fitz.h b/fitz/fitz.h
index ddffa181..7a13ef75 100644
--- a/fitz/fitz.h
+++ b/fitz/fitz.h
@@ -139,134 +139,6 @@ struct fz_error_context_s
void fz_var_imp(void *);
#define fz_var(var) fz_var_imp((void *)&(var))
-/*
-
-MuPDF uses a set of exception handling macros to simplify error return
-and cleanup. Conceptually, they work a lot like C++'s try/catch system,
-but do not require any special compiler support.
-
-The basic formulation is as follows:
-
- fz_try(ctx)
- {
- // Try to perform a task. Never 'return', 'goto' or 'longjmp' out
- // of here. 'break' may be used to safely exit (just) the try block
- // scope.
- }
- fz_always(ctx)
- {
- // Any code here is always executed, regardless of whether an
- // exception was thrown within the try or not. Never 'return', 'goto'
- // or longjmp out from here. 'break' may be used to safely exit (just)
- // the always block scope.
- }
- fz_catch(ctx)
- {
- // This code is called (after any always block) only if something
- // within the fz_try block (including any functions it called) threw
- // an exception. The code here is expected to handle the exception
- // (maybe record/report the error, cleanup any stray state etc) and
- // can then either exit the block, or pass on the exception to a
- // higher level (enclosing) fz_try block (using fz_throw, or
- // fz_rethrow).
- }
-
-The fz_always block is optional, and can safely be omitted.
-
-The macro based nature of this system has 3 main limitations:
-
-1) Never return from within try (or 'goto' or longjmp out of it).
- This upsets the internal housekeeping of the macros and will cause
- problems later on. The code will detect such things happening, but
- by then it is too late to give a helpful error report as to where the
- original infraction occurred.
-
-2) The fz_try(ctx) { ... } fz_always(ctx) { ... } fz_catch(ctx) { ... }
- is not one atomic C statement. That is to say, if you do:
-
- if (condition)
- fz_try(ctx) { ... }
- fz_catch(ctx) { ... }
-
- then you will not get what you want. Use the following instead:
-
- if (condition) {
- fz_try(ctx) { ... }
- fz_catch(ctx) { ... }
- }
-
-3) The macros are implemented using setjmp and longjmp, and so the standard
- C restrictions on the use of those functions apply to fz_try/fz_catch
- too. In particular, any "truly local" variable that is set between the
- start of fz_try and something in fz_try throwing an exception may become
- undefined as part of the process of throwing that exception.
-
- As a way of mitigating this problem, we provide an fz_var() macro that
- tells the compiler to ensure that that variable is not unset by the
- act of throwing the exception.
-
-A model piece of code using these macros then might be:
-
- house build_house(plans *p)
- {
- material m = NULL;
- walls w = NULL;
- roof r = NULL;
- house h = NULL;
- tiles t = make_tiles();
-
- fz_var(w);
- fz_var(r);
- fz_var(h);
-
- fz_try(ctx)
- {
- fz_try(ctx)
- {
- m = make_bricks();
- }
- fz_catch(ctx)
- {
- // No bricks available, make do with straw?
- m = make_straw();
- }
- w = make_walls(m, p);
- r = make_roof(m, t);
- h = combine(w, r); // Note, NOT: return combine(w,r);
- }
- fz_always(ctx)
- {
- drop_walls(w);
- drop_roof(r);
- drop_material(m);
- drop_tiles(t);
- }
- fz_catch(ctx)
- {
- fz_throw(ctx, "build_house failed");
- }
- return h;
- }
-
-Things to note about this:
-
-a) If make_tiles throws an exception, this will immediately be handled
- by some higher level exception handler. If it succeeds, t will be
- set before fz_try starts, so there is no need to fz_var(t);
-
-b) We try first off to make some bricks as our building material. If
- this fails, we fall back to straw. If this fails, we'll end up in
- the fz_catch, and the process will fail neatly.
-
-c) We assume in this code that combine takes new reference to both the
- walls and the roof it uses, and therefore that w and r need to be
- cleaned up in all cases.
-
-d) We assume the standard C convention that it is safe to destroy
- NULL things.
-
-*/
-
/* Exception macro definitions. Just treat these as a black box - pay no
* attention to the man behind the curtain. */