57 lines
2.4 KiB
Diff
57 lines
2.4 KiB
Diff
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From 16d88e7813a7739c070a7a1cf6388fd4f236fd99 Mon Sep 17 00:00:00 2001
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From: Gustavo Zacarias <gustavo@zacarias.com.ar>
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Date: Fri, 31 Jan 2014 06:45:18 -0300
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Subject: [PATCHv2] build: find FILE_OFFSET_BITS via array
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This makes cross-compiling happy, use a trick similar to autoconf's
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AC_CHECK_SIZEOF macro.
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Basically we make an array:
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static int array[1 - 2 * !(((long int)(sizeof(off_t))) < 8)];
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This gives -1 multiplied by the negation of the condition
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(sizeof(off_t) < 8) cast to a long int.
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So if the condition is true it gives array[(-1 * 0)] (remember the
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condition is cast and negated) thus passing a build test with a 0-sized
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array.
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If it's false it gives array[(-1 * 1)] thus failing with a
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negative-sized array.
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Status: upstream for next branch.
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Signed-off-by: Gustavo Zacarias <gustavo@zacarias.com.ar>
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---
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lib/ccan/wscript | 11 +++++++----
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1 file changed, 7 insertions(+), 4 deletions(-)
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diff --git a/lib/ccan/wscript b/lib/ccan/wscript
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index 59b8205..81039d0 100644
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--- a/lib/ccan/wscript
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+++ b/lib/ccan/wscript
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@@ -127,15 +127,18 @@ def configure(conf):
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# Only check for FILE_OFFSET_BITS=64 if off_t is normally small:
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# use raw routines because wrappers include previous _GNU_SOURCE
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# or _FILE_OFFSET_BITS defines.
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+ # The math for these tests is:
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+ # array[-1 * !((int)(condition)) ] (condition is true) = array[0] = builds
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+ # array[-1 * !((int)(condition)) ] (condition is false) = array[-1] = fails
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conf.check(fragment="""#include <sys/types.h>
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- int main(void) { return !(sizeof(off_t) < 8); }""",
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- execute=True, msg='Checking for small off_t',
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+ int main(void) { static int test_array[1 - 2 * !(((long int)(sizeof(off_t))) < 8)]; }""",
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+ msg='Checking for small off_t',
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define_name='SMALL_OFF_T')
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# Unreliable return value above, hence use define.
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if conf.CONFIG_SET('SMALL_OFF_T'):
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conf.check(fragment="""#include <sys/types.h>
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- int main(void) { return !(sizeof(off_t) >= 8); }""",
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- execute=True, msg='Checking for -D_FILE_OFFSET_BITS=64',
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+ int main(void) { static int test_array[1 - 2 * !(((long int)(sizeof(off_t))) >= 8)]; }""",
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+ msg='Checking for -D_FILE_OFFSET_BITS=64',
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ccflags='-D_FILE_OFFSET_BITS=64',
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define_name='HAVE_FILE_OFFSET_BITS')
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--
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1.8.3.2
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