[ViewVC] Diff of: cvs/cvsroot/libecb/ecb.pod

Comparing cvsroot/libecb/ecb.pod (file contents):
Revision 1.51 by root, Thu Jul 19 18:08:58 2012 UTC vs.
Revision 1.62 by root, Wed Feb 18 20:29:27 2015 UTC

…		…
68	platform (currently C<4> or C<8>) and can be used in preprocessor	68	platform (currently C<4> or C<8>) and can be used in preprocessor
69	expressions.	69	expressions.
70		70
71	For C<ptrdiff_t> and C<size_t> use C<stddef.h>.	71	For C<ptrdiff_t> and C<size_t> use C<stddef.h>.
72		72
73	=head2 LANGUAGE/COMPILER VERSIONS	73	=head2 LANGUAGE/ENVIRONMENT/COMPILER VERSIONS
74		74
75	All the following symbols expand to an expression that can be tested in	75	All the following symbols expand to an expression that can be tested in
76	preprocessor instructions as well as treated as a boolean (use C<!!> to	76	preprocessor instructions as well as treated as a boolean (use C<!!> to
77	ensure it's either C<0> or C<1> if you need that).	77	ensure it's either C<0> or C<1> if you need that).
78		78
79	=over 4	79	=over 4
80		80
81	=item ECB_C	81	=item ECB_C
82		82
83	True if the implementation defines the C<__STDC__> macro to a true value,	83	True if the implementation defines the C<__STDC__> macro to a true value,
84	which is typically true for both C and C++ compilers.	84	while not claiming to be C++.
85		85
86	=item ECB_C99	86	=item ECB_C99
87		87
88	True if the implementation claims to be compliant to C99 (ISO/IEC	88	True if the implementation claims to be compliant to C99 (ISO/IEC
89	9899:1999) or any later version.	89	9899:1999) or any later version, while not claiming to be C++.
90		90
91	Note that later versions (ECB_C11) remove core features again (for	91	Note that later versions (ECB_C11) remove core features again (for
92	example, variable length arrays).	92	example, variable length arrays).
93		93
94	=item ECB_C11	94	=item ECB_C11
95		95
96	True if the implementation claims to be compliant to C11 (ISO/IEC	96	True if the implementation claims to be compliant to C11 (ISO/IEC
97	9899:2011) or any later version.	97	9899:2011) or any later version, while not claiming to be C++.
98		98
99	=item ECB_CPP	99	=item ECB_CPP
100		100
101	True if the implementation defines the C<__cplusplus__> macro to a true	101	True if the implementation defines the C<__cplusplus__> macro to a true
102	value, which is typically true for C++ compilers.	102	value, which is typically true for C++ compilers.
…		…
104	=item ECB_CPP11	104	=item ECB_CPP11
105		105
106	True if the implementation claims to be compliant to ISO/IEC 14882:2011	106	True if the implementation claims to be compliant to ISO/IEC 14882:2011
107	(C++11) or any later version.	107	(C++11) or any later version.
108		108
109	=item ECB_GCC_VERSION(major,minor)	109	=item ECB_GCC_VERSION (major, minor)
110		110
111	Expands to a true value (suitable for testing in by the preprocessor)	111	Expands to a true value (suitable for testing in by the preprocessor)
112	if the compiler used is GNU C and the version is the given version, or	112	if the compiler used is GNU C and the version is the given version, or
113	higher.	113	higher.
114		114
…		…
150		150
151	This is true for basically all modern platforms, although F<ecb.h> might	151	This is true for basically all modern platforms, although F<ecb.h> might
152	not be able to deduce this correctly everywhere and might err on the safe	152	not be able to deduce this correctly everywhere and might err on the safe
153	side.	153	side.
154		154
		155	=item ECB_AMD64, ECB_AMD64_X32
		156
		157	These two macros are defined to C<1> on the x86_64/amd64 ABI and the X32
		158	ABI, respectively, and undefined elsewhere.
		159
		160	The designers of the new X32 ABI for some inexplicable reason decided to
		161	make it look exactly like amd64, even though it's completely incompatible
		162	to that ABI, breaking about every piece of software that assumed that
		163	C<__x86_64> stands for, well, the x86-64 ABI, making these macros
		164	necessary.
		165
155	=back	166	=back
156		167
		168	=head2 MACRO TRICKERY
		169
		170	=over 4
		171
		172	=item ECB_CONCAT (a, b)
		173
		174	Expands any macros in C<a> and C<b>, then concatenates the result to form
		175	a single token. This is mainly useful to form identifiers from components,
		176	e.g.:
		177
		178	#define S1 str
		179	#define S2 cpy
		180
		181	ECB_CONCAT (S1, S2)(dst, src); // == strcpy (dst, src);
		182
		183	=item ECB_STRINGIFY (arg)
		184
		185	Expands any macros in C<arg> and returns the stringified version of
		186	it. This is mainly useful to get the contents of a macro in string form,
		187	e.g.:
		188
		189	#define SQL_LIMIT 100
		190	sql_exec ("select * from table limit " ECB_STRINGIFY (SQL_LIMIT));
		191
		192	=back
		193
157	=head2 GCC ATTRIBUTES	194	=head2 ATTRIBUTES
158		195
159	A major part of libecb deals with GCC attributes. These are additional	196	A major part of libecb deals with additional attributes that can be
160	attributes that you can assign to functions, variables and sometimes even	197	assigned to functions, variables and sometimes even types - much like
161	types - much like C<const> or C<volatile> in C.	198	C<const> or C<volatile> in C. They are implemented using either GCC
162		199	attributes or other compiler/language specific features. Attributes
163	While GCC allows declarations to show up in many surprising places,
164	but not in many expected places, the safest way is to put attribute
165	declarations before the whole declaration:	200	declarations must be put before the whole declaration:
166		201
167	ecb_const int mysqrt (int a);	202	ecb_const int mysqrt (int a);
168	ecb_unused int i;	203	ecb_unused int i;
169		204
170	For variables, it is often nicer to put the attribute after the name, and
171	avoid multiple declarations using commas:
172
173	int i ecb_unused;
174
175	=over 4	205	=over 4
176
177	=item ecb_attribute ((attrs...))
178
179	A simple wrapper that expands to C<__attribute__((attrs))> on GCC, and to
180	nothing on other compilers, so the effect is that only GCC sees these.
181
182	Example: use the C<deprecated> attribute on a function.
183
184	ecb_attribute((__deprecated__)) void
185	do_not_use_me_anymore (void);
186		206
187	=item ecb_unused	207	=item ecb_unused
188		208
189	Marks a function or a variable as "unused", which simply suppresses a	209	Marks a function or a variable as "unused", which simply suppresses a
190	warning by GCC when it detects it as unused. This is useful when you e.g.	210	warning by GCC when it detects it as unused. This is useful when you e.g.
191	declare a variable but do not always use it:	211	declare a variable but do not always use it:
192		212
193	{	213	{
194	int var ecb_unused;	214	ecb_unused int var;
195		215
196	#ifdef SOMECONDITION	216	#ifdef SOMECONDITION
197	var = ...;	217	var = ...;
198	return var;	218	return var;
199	#else	219	#else
200	return 0;	220	return 0;
201	#endif	221	#endif
202	}	222	}
203		223
		224	=item ecb_deprecated
		225
		226	Similar to C<ecb_unused>, but marks a function, variable or type as
		227	deprecated. This makes some compilers warn when the type is used.
		228
		229	=item ecb_deprecated_message (message)
		230
		231	Same as C<ecb_deprecated>, but if possible, supply a diagnostic that is
		232	used instead of a generic depreciation message when the object is being
		233	used.
		234
204	=item ecb_inline	235	=item ecb_inline
205		236
206	This is not actually an attribute, but you use it like one. It expands
207	either to C<static inline> or to just C<static>, if inline isn't	237	Expands either to C<static inline> or to just C<static>, if inline
208	supported. It should be used to declare functions that should be inlined,	238	isn't supported. It should be used to declare functions that should be
209	for code size or speed reasons.	239	inlined, for code size or speed reasons.
210		240
211	Example: inline this function, it surely will reduce codesize.	241	Example: inline this function, it surely will reduce codesize.
212		242
213	ecb_inline int	243	ecb_inline int
214	negmul (int a, int b)	244	negmul (int a, int b)
…		…
236	}	266	}
237		267
238	In this case, the compiler would probably be smart enough to deduce it on	268	In this case, the compiler would probably be smart enough to deduce it on
239	its own, so this is mainly useful for declarations.	269	its own, so this is mainly useful for declarations.
240		270
		271	=item ecb_restrict
		272
		273	Expands to the C<restrict> keyword or equivalent on compilers that support
		274	them, and to nothing on others. Must be specified on a pointer type or
		275	an array index to indicate that the memory doesn't alias with any other
		276	restricted pointer in the same scope.
		277
		278	Example: multiply a vector, and allow the compiler to parallelise the
		279	loop, because it knows it doesn't overwrite input values.
		280
		281	void
		282	multiply (ecb_restrict float *src,
		283	ecb_restrict float *dst,
		284	int len, float factor)
		285	{
		286	int i;
		287
		288	for (i = 0; i < len; ++i)
		289	dst [i] = src [i] * factor;
		290	}
		291
241	=item ecb_const	292	=item ecb_const
242		293
243	Declares that the function only depends on the values of its arguments,	294	Declares that the function only depends on the values of its arguments,
244	much like a mathematical function. It specifically does not read or write	295	much like a mathematical function. It specifically does not read or write
245	any memory any arguments might point to, global variables, or call any	296	any memory any arguments might point to, global variables, or call any
…		…
305	functions only called in exceptional or rare cases.	356	functions only called in exceptional or rare cases.
306		357
307	=item ecb_artificial	358	=item ecb_artificial
308		359
309	Declares the function as "artificial", in this case meaning that this	360	Declares the function as "artificial", in this case meaning that this
310	function is not really mean to be a function, but more like an accessor	361	function is not really meant to be a function, but more like an accessor
311	- many methods in C++ classes are mere accessor functions, and having a	362	- many methods in C++ classes are mere accessor functions, and having a
312	crash reported in such a method, or single-stepping through them, is not	363	crash reported in such a method, or single-stepping through them, is not
313	usually so helpful, especially when it's inlined to just a few instructions.	364	usually so helpful, especially when it's inlined to just a few instructions.
314		365
315	Marking them as artificial will instruct the debugger about just this,	366	Marking them as artificial will instruct the debugger about just this,
…		…
335		386
336	=head2 OPTIMISATION HINTS	387	=head2 OPTIMISATION HINTS
337		388
338	=over 4	389	=over 4
339		390
340	=item bool ecb_is_constant(expr)	391	=item bool ecb_is_constant (expr)
341		392
342	Returns true iff the expression can be deduced to be a compile-time	393	Returns true iff the expression can be deduced to be a compile-time
343	constant, and false otherwise.	394	constant, and false otherwise.
344		395
345	For example, when you have a C<rndm16> function that returns a 16 bit	396	For example, when you have a C<rndm16> function that returns a 16 bit
…		…
363	return is_constant (n) && !(n & (n - 1))	414	return is_constant (n) && !(n & (n - 1))
364	? rndm16 () & (num - 1)	415	? rndm16 () & (num - 1)
365	: (n * (uint32_t)rndm16 ()) >> 16;	416	: (n * (uint32_t)rndm16 ()) >> 16;
366	}	417	}
367		418
368	=item bool ecb_expect (expr, value)	419	=item ecb_expect (expr, value)
369		420
370	Evaluates C<expr> and returns it. In addition, it tells the compiler that	421	Evaluates C<expr> and returns it. In addition, it tells the compiler that
371	the C<expr> evaluates to C<value> a lot, which can be used for static	422	the C<expr> evaluates to C<value> a lot, which can be used for static
372	branch optimisations.	423	branch optimisations.
373		424
…		…
420	{	471	{
421	if (ecb_expect_false (current + size > end))	472	if (ecb_expect_false (current + size > end))
422	real_reserve_method (size); /* presumably noinline */	473	real_reserve_method (size); /* presumably noinline */
423	}	474	}
424		475
425	=item bool ecb_assume (cond)	476	=item ecb_assume (cond)
426		477
427	Try to tell the compiler that some condition is true, even if it's not	478	Try to tell the compiler that some condition is true, even if it's not
428	obvious.	479	obvious.
429		480
430	This can be used to teach the compiler about invariants or other	481	This can be used to teach the compiler about invariants or other
…		…
450		501
451	Then the compiler I<might> be able to optimise out the second call	502	Then the compiler I<might> be able to optimise out the second call
452	completely, as it knows that C<< current + 1 > end >> is false and the	503	completely, as it knows that C<< current + 1 > end >> is false and the
453	call will never be executed.	504	call will never be executed.
454		505
455	=item bool ecb_unreachable ()	506	=item ecb_unreachable ()
456		507
457	This function does nothing itself, except tell the compiler that it will	508	This function does nothing itself, except tell the compiler that it will
458	never be executed. Apart from suppressing a warning in some cases, this	509	never be executed. Apart from suppressing a warning in some cases, this
459	function can be used to implement C<ecb_assume> or similar functions.	510	function can be used to implement C<ecb_assume> or similar functions.
460		511
461	=item bool ecb_prefetch (addr, rw, locality)	512	=item ecb_prefetch (addr, rw, locality)
462		513
463	Tells the compiler to try to prefetch memory at the given C<addr>ess	514	Tells the compiler to try to prefetch memory at the given C<addr>ess
464	for either reading (C<rw> = 0) or writing (C<rw> = 1). A C<locality> of	515	for either reading (C<rw> = 0) or writing (C<rw> = 1). A C<locality> of
465	C<0> means that there will only be one access later, C<3> means that	516	C<0> means that there will only be one access later, C<3> means that
466	the data will likely be accessed very often, and values in between mean	517	the data will likely be accessed very often, and values in between mean
…		…
615		666
616	=head2 FLOATING POINT FIDDLING	667	=head2 FLOATING POINT FIDDLING
617		668
618	=over 4	669	=over 4
619		670
		671	=item ECB_INFINITY
		672
		673	Evaluates to positive infinity if supported by the platform, otherwise to
		674	a truly huge number.
		675
		676	=item ECB_NON
		677
		678	Evaluates to a quiet NAN if supported by the platform, otherwise to
		679	C<ECB_INFINITY>.
		680
		681	=item float ecb_ldexpf (float x, int exp)
		682
		683	Same as C<ldexpf>, but always available.
		684
620	=item uint32_t ecb_float_to_binary32 (float x) [-UECB_NO_LIBM]	685	=item uint32_t ecb_float_to_binary32 (float x) [-UECB_NO_LIBM]
621		686
622	=item uint64_t ecb_double_to_binary64 (double x) [-UECB_NO_LIBM]	687	=item uint64_t ecb_double_to_binary64 (double x) [-UECB_NO_LIBM]
623		688
624	These functions each take an argument in the native C<float> or C<double>	689	These functions each take an argument in the native C<float> or C<double>
…		…
647	/* this results in a single add instruction to toggle the bit, and 4 extra */	712	/* this results in a single add instruction to toggle the bit, and 4 extra */
648	/* instructions to move the float value to an integer register and back. */	713	/* instructions to move the float value to an integer register and back. */
649		714
650	x = ecb_binary32_to_float (ecb_float_to_binary32 (x) ^ 0x80000000U)	715	x = ecb_binary32_to_float (ecb_float_to_binary32 (x) ^ 0x80000000U)
651		716
		717	=item float ecb_binary16_to_float (uint16_t x) [-UECB_NO_LIBM]
		718
652	=item float ecb_binary32_to_float (uint32_t x) [-UECB_NO_LIBM]	719	=item float ecb_binary32_to_float (uint32_t x) [-UECB_NO_LIBM]
653		720
654	=item double ecb_binary32_to_double (uint64_t x) [-UECB_NO_LIBM]	721	=item double ecb_binary32_to_double (uint64_t x) [-UECB_NO_LIBM]
655		722
656	The reverse operation of the previos function - takes the bit representation	723	The reverse operation of the previous function - takes the bit
657	of an IEEE binary32 or binary64 number and converts it to the native C<float>	724	representation of an IEEE binary16, binary32 or binary64 number and
658	or C<double> format.	725	converts it to the native C<float> or C<double> format.
659		726
660	This function should work even when the native floating point format isn't	727	This function should work even when the native floating point format isn't
661	IEEE compliant, of course at a speed and code size penalty, and of course	728	IEEE compliant, of course at a speed and code size penalty, and of course
662	also within reasonable limits (it tries to convert normals and denormals,	729	also within reasonable limits (it tries to convert normals and denormals,
663	and might be lucky for infinities, and with extraordinary luck, also for	730	and might be lucky for infinities, and with extraordinary luck, also for

Diff Legend

-–
+Removed lines
-+
+Added lines
-<
+Changed lines
->
+Changed lines

Comparing cvsroot/libecb/ecb.pod (file contents): Revision 1.51 by root, Thu Jul 19 18:08:58 2012 UTC vs. Revision 1.62 by root, Wed Feb 18 20:29:27 2015 UTC

Diff Legend

Comparing cvsroot/libecb/ecb.pod (file contents):
Revision 1.51 by root, Thu Jul 19 18:08:58 2012 UTC vs.
Revision 1.62 by root, Wed Feb 18 20:29:27 2015 UTC