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82 lines
3.2 KiB
Plaintext
82 lines
3.2 KiB
Plaintext
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dnl macro AST_CHECK_STRSEP_ARRAY_BOUNDS0
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dnl
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dnl The optimized strcmp and strsep macro's in
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dnl /usr/include/xxx-linux-gnu/bits/string2.h produce a warning (-Warray-bounds)
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dnl when compiled with clang (+ -O1), when the delimiter parameter is
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dnl passed in as a char *, instead of the expected char[]
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dnl
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dnl Instead of replacing all occurrences of strsep and strcmp, looking like:
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dnl xxx_name = strsep(&rest, ",");
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dnl
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dnl with:
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dnl char delimiters[] = ",";
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dnl xxx_name = strsep(&rest, delimiters);
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dnl
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dnl to get around this warning, without having to suppress the warning completely.
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dnl This macro detects the warning and force these 'optimizations' to be
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dnl switched off (Clang already has a set of builtin optimizers which should result
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dnl in good performance for these type of functions).
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dnl
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dnl When the issue is detected it will add a define to autoconfig.h which will prevent
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dnl bits/string2.h from replacing the standard implementation of strsep/strcmp with it's
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dnl macro optimized version. bits/string.h checks these defines before inserting it's
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dnl replacements.
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dnl
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dnl When bits/string2.h get's fixed in the future, this macro should be able to
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dnl detect the new behaviour, and when no warning is generated, it will use the optimize
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dnl version from bits/string2.h
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dnl
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dnl
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dnl See 'define __strcmp_gc(s1, s2, l2) in bits/string2.h'
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dnl
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dnl llvm-comment: Normally, this array-bounds warning are suppressed for macros, so that
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dnl unused paths like the one that accesses __s1[3] are not warned about. But if you
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dnl preprocess manually, and feed the result to another instance of clang, it will warn
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dnl about all the possible forks of this particular if statement.
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dnl
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dnl Instead of switching of this optimization, another solution would be to run the pre-
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dnl processing step with -frewrite-includes, which should preserve enough information
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dnl so that clang should still be able to suppress the diagnostic at the compile step
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dnl later on.
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dnl
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dnl See also "https://llvm.org/bugs/show_bug.cgi?id=20144"
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dnl See also "https://llvm.org/bugs/show_bug.cgi?id=11536"
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dnl
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AC_DEFUN([AST_CHECK_STRSEP_ARRAY_BOUNDS], [
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AC_MSG_CHECKING([for clang strsep/strcmp optimization])
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save_CFLAGS="$CFLAGS"
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CFLAGS="$CFLAGS -O1 -Werror=array-bounds"
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AC_COMPILE_IFELSE(
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[
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AC_LANG_SOURCE([
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#include <stdio.h>
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#include <string.h>
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/* fails with clang and -O1 */
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void test_strsep_strcmp (void) {
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char *haystackstr = "test1,test2";
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char *outstr;
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if (!strcmp(haystackstr, ",")) {
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printf("fail\n");
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}
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if ((outstr = strsep(&haystackstr, ","))) {
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printf("fail:%s\n", outstr);
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}
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}
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int main(int argc, char *argv[]) {
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test_strsep_strcmp();
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return 0;
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}
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])
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],[
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AC_MSG_RESULT(no)
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],[
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dnl setting this define in autoconfig.h will prevent bits/string2.h from replacing the standard implementation of strsep/strcmp
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AC_DEFINE([_HAVE_STRING_ARCH_strcmp], 1, [Prevent clang array-bounds warning by not using strcmp from bits/string2.h])
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AC_DEFINE([_HAVE_STRING_ARCH_strsep], 1, [Prevent clang array-bounds warning by not using strsep from bits/string2.h])
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AC_MSG_RESULT([prevent use of __string2_1bptr_p / strsep / strcmp from bits/string2.h])
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]
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)
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CFLAGS="$save_CFLAGS"
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])
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