[Valgrind-developers] [valgrind] Darwin initimg: fix location for start of stringtable on x86

[Paul F. <pa...@so...>]

https://sourceware.org/cgit/valgrind/commit/?id=48d1e600f156550489c8ed11ccf236d333b8de8d

commit 48d1e600f156550489c8ed11ccf236d333b8de8d
Author: Paul Floyd <pj...@wa...>
Date:   Wed Mar 11 22:02:49 2026 +0100

    Darwin initimg: fix location for start of stringtable on x86
    
    I was calculating the remainder (%16) rather than the amount needed
    to round up to the next multiple of 16. That worked on amd64
    where it is 0 or 8 either way. On x86 4 and 12 were the wrong
    way round.

Diff:
---
 coregrind/m_initimg/initimg-darwin.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/coregrind/m_initimg/initimg-darwin.c b/coregrind/m_initimg/initimg-darwin.c
index 5ef2269fee..b65ab4f5a9 100644
--- a/coregrind/m_initimg/initimg-darwin.c
+++ b/coregrind/m_initimg/initimg-darwin.c
@@ -444,7 +444,7 @@ Addr setup_client_stack( void*  init_sp,
       rounding up stringsize to a multiple of sizeof(Word) plus rounding of the whole
       from a multiple of sizeof(Word) to a multiple of 16. Need to keep both of these
       in order to calculate stringbase. */
-   size_t pointer_slop = stacksize % 16;
+   size_t pointer_slop = VG_ROUNDUP(stacksize, 16) - stacksize;
    stacksize = VG_ROUNDUP(stacksize, 16);
 
    if (0) VG_(printf)("stacksize = %u\n", stacksize);