Fix for bug #31207: Test "join_nested" shows different strategy on IA64

CPUs / Intel's ICC compile

The bug is a combination of two problems:

1. IA64/ICC MySQL binaries use glibc's qsort(), not the one in mysys.

2. The order relation implemented by join_tab_cmp() is not transitive,
i.e. it is possible to choose such a, b and c that (a < b) && (b < c)
but (c < a). This implies that result of a sort using the relation
implemented by join_tab_cmp() depends on the order in which
elements are compared, i.e. the result is implementation-specific. Since
choose_plan() uses qsort() to pre-sort the
join tables using join_tab_cmp() as a compare function, the results of
the sorting may vary depending on qsort() implementation.

It is neither possible nor important to implement a better ordering
algorithm in join_tab_cmp(). Therefore the only way to fix it is to
force our own qsort() to be used by renaming it to my_qsort(), so we don't depend
on linker to decide that.

This patch also "fixes" bug #20530: qsort redefinition violates the
standard.

1 files changed, 4 insertions, 2 deletions

diff --git a/include/my_sys.h b/include/my_sys.h
index 4f7e75a836e..d401cfca082 100644
--- a/include/my_sys.h
+++ b/include/my_sys.h
@@ -709,8 +709,10 @@ extern sig_handler my_set_alarm_variable(int signo);
 extern void my_string_ptr_sort(void *base,uint items,size_s size);
 extern void radixsort_for_str_ptr(uchar* base[], uint number_of_elements,
 				  size_s size_of_element,uchar *buffer[]);
-extern qsort_t qsort2(void *base_ptr, size_t total_elems, size_t size,
-		      qsort2_cmp cmp, void *cmp_argument);
+extern qsort_t my_qsort(void *base_ptr, size_t total_elems, size_t size,
+                        qsort_cmp cmp);
+extern qsort_t my_qsort2(void *base_ptr, size_t total_elems, size_t size,
+                         qsort2_cmp cmp, void *cmp_argument);
 extern qsort2_cmp get_ptr_compare(uint);
 void my_store_ptr(byte *buff, uint pack_length, my_off_t pos);
 my_off_t my_get_ptr(byte *ptr, uint pack_length);