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math/mpreduce.h: Missing include files.
[u/mdw/catacomb] / m4 / mdw-probe-constant.m4
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MW		 1dnl -*-autoconf-*-
2
3### SYNOPSIS
4###
5### mdw_PROBE_CONSTANT(VAR, EXPR, [PREAMBLE], [IF-FAILED])
6###
7### DESCRIPTION
8###
9### Extracts the value of a a constant integer expression from the
10### compiler. This works even if the compiler in question doesn't target
11### the current architecture. The value must be in the range -10^244 < x <
12### 10^244; this is probably fair enough. In the extraordinarily unliklely
13### event that the constant value is outside these bounds, the macro will
14### fail rather than silently giving a wrong answer.
15###
16### The result of the macro is that the shell variable VAR has the value of
17### the expression EXPR, in decimal. The PREAMBLE, if given, is inserted
18### before EXPR is evaluated; it should contain #include and #define
19### directives which are used to compute the value of the expression.
20###
21### The idea for this macro came from the AC_C_COMPILE_VALUE macro by
22### Ilguiz Latypov; this implementation has a number of advantages:
23###
24### * it has an immense range of representable values, notably including
25### negative numbers; and
26###
27### * it returns the value directly in a shell variable rather than
28### inventing an AC_DEFINE for it.
29###
30### LICENSE
31###
32### Copyright (c) 2013 Mark Wooding <mdw@distorted.org.uk>
33###
34### This program is free software: you can redistribute it and/or modify it
35### under the terms of the GNU General Public License as published by the
36### Free Software Foundation, either version 2 of the License, or (at your
37### option) any later version.
38###
39### This program is distributed in the hope that it will be useful, but
40### WITHOUT ANY WARRANTY; without even the implied warranty of
41### MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
42### General Public License for more details.
43###
44### You should have received a copy of the GNU General Public License along
45### with this program. If not, see <http://www.gnu.org/licenses/>.
46###
47### In particular, no exception to the GPL is granted regarding generated
48### `configure' scripts which are the output of Autoconf.
49
50# Serial 1
51AC_COPYRIGHT([
52Portions copyright (c) 2013 Mark Wooding.
53
54This configure script is free software: you can redistribute it and/or
55modify it under he terms of the GNU General Public License as published
56by the Free Software Foundation, either version 2 of the License, or
57(at your option) any later version.])
58
59AC_DEFUN([mdw__PROBE_CONSTANT_SETUP],
60 [mdw__probe_constant_body="[
61
62/* The following program is copyright (c) 2013 Mark Wooding. It is free
63 * software: you can redistribute it and/or modify it under the terms of the
64 * GNU General Public License as published by the Free Software Foundation,
65 * either version 2 of the License, or (at your option) any later version.
66 *
67 * This program is distributed in the hope that it will be useful, but
68 * WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
69 * or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
70 * for more details.
71 *
72 * You should have received a copy of the GNU General Public License along
73 * with this program. If not, see <http://www.gnu.org/licenses/>.
74 */
75
76/* The constant: 1 billion. We'll pull digits out in groups of nine, since
77 * we can work with constants of at least the size of a C \`long'.
78 */
79#define MDW__G 1000000000
80
81/* An empty macro, used as an argument sometimes. */
82#define MDW__E
83
84/* A cheesy compile-time assertion. If X is zero, then we try to declare
85 * an array with a negative number of elements. Wrap this up in an anonymous
86 * struct so that we don't have to worry about naming things if we make
87 * more than one assertion.
88 */
89#define MDW__ASSERT(x) struct { int v[1 - 2*!(x)]; }
90
91/* Return the value of X/DIV, with further divisions D applied, truncating
92 * towards zero. DIV must be greater than one. This works even if X is
93 * negative, never tries to divide negative numbers, and doesn't try to
94 * negate the most-negative value. There are three cases: if X <= -DIV then
95 * X/DIV = -(X + DIV)/DIV - 1, and X + DIV is less negative than X so this is
96 * a safe negation; if -DIV < X < 0 then the result is zero; otherwise, X
97 * is nonnegative so the straightforward division is safe. Because DIV > 1,
98 * X/DIV is safe to negate, and we can apply the remaining divisions to it.
99 */
100#define MDW__SHIFT(x, div, d) \\
101 ((x) >= 0 ? ((x)/div d) : \\
102 (x) <= -(div) ? -((-((x) + (div))/(div) + 1) d) : 0)
103
104/* Extract the bottommost digit of X, as an integer: i.e., the value of
105 * abs(X) mod 10. This works even if X is negative, never tries to divide
106 * negative numbers, and doesn't try to divide the most-negative value.
107 */
108#define MDW__RAW_DIGIT(x) (((x) < 0 ? -((x) + 1) % 10 + 1 : (x)) % 10)
109
110/* Extract the bottommost digit of X, as a character; if X is zero, then
111 * produce a space instead. This avoids leading zeroes which can be
112 * misinterpreted by callers.
113 */
114#define MDW__TEXT_DIGIT(x) ((x) ? '0' + MDW__RAW_DIGIT(x) : ' ')
115
116/* Extract the bottommost digit of the probe value, after dividing by DIV
117 * and applying the divisons D.
118 */
119#define MDW__DIGIT(div, d) \\
120 MDW__TEXT_DIGIT(MDW__SHIFT(MDW__PROBE_EXPR, div, d))
121
122/* Extract the bottommost six digits of the probe value after dividing by 10
123 * and then applying the divisions D.
124 */
125#define MDW__9DIGITS(d) \\
126 MDW__DIGIT(1000000000, d), \\
127 MDW__DIGIT( 100000000, d), \\
128 MDW__DIGIT( 10000000, d), \\
129 MDW__DIGIT( 1000000, d), \\
130 MDW__DIGIT( 100000, d), \\
131 MDW__DIGIT( 10000, d), \\
132 MDW__DIGIT( 1000, d), \\
133 MDW__DIGIT( 100, d), \\
134 MDW__DIGIT( 10, d)
135
136/* Increasingly huge divisions. PN divides by 10^(9*2^N). */
137#define MDW__P0 /MDW__G
138#define MDW__P1 MDW__P0 MDW__P0
139#define MDW__P2 MDW__P1 MDW__P1
140#define MDW__P3 MDW__P2 MDW__P2
141#define MDW__P4 MDW__P3 MDW__P3
142#define MDW__P5 MDW__P4 MDW__P4
143
144/* Increasingly long sequences of digits. DN(P) produces the 9 * 2^N
145 * digits after applying divisions P.
146 */
147#define MDW__D0(p) MDW__9DIGITS(p MDW__P0), MDW__9DIGITS(p MDW__E)
148#define MDW__D1(p) MDW__D0(p MDW__P1), MDW__D0(p)
149#define MDW__D2(p) MDW__D1(p MDW__P2), MDW__D1(p)
150#define MDW__D3(p) MDW__D2(p MDW__P3), MDW__D2(p)
151#define MDW__D4(p) MDW__D3(p MDW__P4), MDW__D3(p)
152
153/* Ensure that our exponential cascade is sufficient to represent the
154 * expression.
155 */
156MDW__ASSERT(MDW__SHIFT(MDW__PROBE_EXPR, 10, MDW__P5) == 0);
157
158/* Format the output. Everything is taken care of except the bottommost
159 * digit, which we handle seaprately because we actually want a \`leading'
160 * zero here if the constant value is actually zero. Format it so that
161 * we can extract it from the object file.
162 */
163const char mdw__probe_output[] = {
164 '\\n',
165 'm', 'd', 'w', '-',
166 'p', 'r', 'o', 'b', 'e', '-',
167 'v', 'a', 'l', 'u', 'e', '=', '\"',
168 (MDW__PROBE_EXPR < 0 ? '-' : ' '),
169 MDW__D4(MDW__E),
170 '0' + MDW__RAW_DIGIT(MDW__PROBE_EXPR),
171 '\"', '\\n'
172};]"])
173
174AC_DEFUN([mdw_PROBE_CONSTANT],
175 [AC_REQUIRE([mdw__PROBE_CONSTANT_SETUP])
176 AC_COMPILE_IFELSE([AC_LANG_SOURCE([[$3
177#define MDW__PROBE_EXPR ($2)
178$mdw__probe_constant_body]])],
179 [$1=$(sed -n \
180 's:^mdw-probe-value="\(-\|\) *\([[0-9]]*\)"$:\1\2:p' conftest.o)],
181 [m4_if([$4], [],
182 [AC_MSG_FAILURE([failed to evaluate expression])],
183 [$4])])])
Catacomb cryptographic library (downstream of http://git.distorted.org.uk/~mdw/catacomb/)