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[PATCH 1/4] qsort_chk: call from gcc_qsort instead of wrapping it


Hi,

This is an independently useful patch that makes it easier to introduce
gcc_stablesort.

Swap responsibilities of gcc_qsort and qsort_chk: call the checking function
from the sorting function instead of wrapping gcc_qsort with qsort_chk.

	* gcc/sort.cc (gcc_qsort) [CHECKING_P]: Call qsort_chk.
	* gcc/system.h (qsort): Always redirect to gcc_qsort.  Update comment.
	* gcc/vec.c (qsort_chk): Do not call gcc_qsort.  Update comment.

diff --git a/gcc/sort.cc b/gcc/sort.cc
index 293e2058f89..9f8ee12e13b 100644
--- a/gcc/sort.cc
+++ b/gcc/sort.cc
@@ -229,4 +229,7 @@ gcc_qsort (void *vbase, size_t n, size_t size, cmp_fn *cmp)
   mergesort (base, &c, n, base, (char *)buf);
   if (buf != scratch)
     free (buf);
+#if CHECKING_P
+  qsort_chk (vbase, n, size, cmp);
+#endif
 }
diff --git a/gcc/system.h b/gcc/system.h
index f87fbaae69e..203c6a4f0cf 100644
--- a/gcc/system.h
+++ b/gcc/system.h
@@ -1197,17 +1197,13 @@ helper_const_non_const_cast (const char *p)
 /* Get definitions of HOST_WIDE_INT.  */
 #include "hwint.h"
 
-/* qsort comparator consistency checking: except in release-checking compilers,
-   redirect 4-argument qsort calls to qsort_chk; keep 1-argument invocations
+/* GCC qsort API-compatible functions: except in release-checking compilers,
+   redirect 4-argument qsort calls to gcc_qsort; keep 1-argument invocations
    corresponding to vec::qsort (cmp): they use C qsort internally anyway.  */
 void qsort_chk (void *, size_t, size_t, int (*)(const void *, const void *));
 void gcc_qsort (void *, size_t, size_t, int (*)(const void *, const void *));
 #define PP_5th(a1, a2, a3, a4, a5, ...) a5
 #undef qsort
-#if CHECKING_P
-#define qsort(...) PP_5th (__VA_ARGS__, qsort_chk, 3, 2, qsort, 0) (__VA_ARGS__)
-#else
 #define qsort(...) PP_5th (__VA_ARGS__, gcc_qsort, 3, 2, qsort, 0) (__VA_ARGS__)
-#endif
 
 #endif /* ! GCC_SYSTEM_H */
diff --git a/gcc/vec.c b/gcc/vec.c
index beb857fd838..ac3226b5fcb 100644
--- a/gcc/vec.c
+++ b/gcc/vec.c
@@ -201,21 +201,12 @@ qsort_chk_error (const void *p1, const void *p2, const void *p3,
   internal_error ("qsort checking failed");
 }
 
-/* Wrapper around qsort with checking that CMP is consistent on given input.
-
-   Strictly speaking, passing invalid (non-transitive, non-anti-commutative)
-   comparators to libc qsort can result in undefined behavior.  Therefore we
-   should ideally perform consistency checks prior to invoking qsort, but in
-   order to do that optimally we'd need to sort the array ourselves beforehand
-   with a sorting routine known to be "safe".  Instead, we expect that most
-   implementations in practice will still produce some permutation of input
-   array even for invalid comparators, which enables us to perform checks on
-   the output array.  */
+/* Verify anti-symmetry and transitivity for comparator CMP on sorted array
+   of N SIZE-sized elements pointed to by BASE.  */
 void
 qsort_chk (void *base, size_t n, size_t size,
 	   int (*cmp)(const void *, const void *))
 {
-  gcc_qsort (base, n, size, cmp);
 #if 0
 #define LIM(n) (n)
 #else
-- 
2.13.3


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