[nginx] Configure: adjusted optimization level for Sun C.

[Maxim Dounin]

details:   http://freenginx.org/hg/nginx/rev/92e14ce71b72
branches:  
changeset: 9309:92e14ce71b72
user:      Maxim Dounin <mdounin at mdounin.ru>
date:      Wed Aug 07 03:56:23 2024 +0300
description:
Configure: adjusted optimization level for Sun C.

With "-fast" (and with "-xbuiltin=%all -xO4"), Sun C miscompiles
ngx_http_script_add_copy_code(), which is inlined into
ngx_http_script_compile().  From the assembly code it looks like
the code uses uninitialized register when calculating new p value
after memcpy:

movq %r15,%rdi
call _memcpy
leaq (%r15,rbx),%rax
movq (%r12),%rbx
movb $0x0000000000000000,(%rax)

Note that %rax is set to (%r15 + %rbx), but %rbx is only set after
it is used.  As such, "*p = '\0'" tries to modify an unrelated memory
address, leading to a segmentation fault.

The issue was seen in tests which use null-terminated complex values:
proxy_ssl_certificate_vars.t, uwsgi_ssl_certificate_vars.t,
stream_proxy_ssl_certificate_vars.t.  Tested with Sun C compilers
from Sun Studio 12.3, 12.4, 12.5, and 12.6.

Restructuring code, such as splitting ngx_cpymem() with a separate
"p += value->len" increment, fixes things, but it is not clear if its
the only place where such miscompilation can happen.

Fix is to use "-fast -xO3".  Since IPO requires "-xO5", it is commented
out.

diffstat:

 auto/cc/sunc |  8 +++++---
 1 files changed, 5 insertions(+), 3 deletions(-)

diffs (23 lines):

diff --git a/auto/cc/sunc b/auto/cc/sunc
--- a/auto/cc/sunc
+++ b/auto/cc/sunc
@@ -73,14 +73,16 @@ MODULE_LINK="-G"
 # 20736 == 0x5100, Sun Studio 12.1
 
 if [ "$ngx_sunc_ver" -ge 20736 ]; then
-    ngx_fast="-fast"
+    ngx_fast="-fast -xO3"
 
 else
     # older versions had problems with bit-fields
-    ngx_fast="-fast -xalias_level=any"
+    ngx_fast="-fast -xO3 -xalias_level=any"
 fi
 
-IPO=-xipo
+IPO=
+#IPO=-xipo
+
 CFLAGS="$CFLAGS $ngx_fast $IPO"
 CORE_LINK="$CORE_LINK $ngx_fast $IPO"