[gcc r16-6485] [PATCH v2]: pch, target: update host hooks for NetBSD and OpenBSD

[Jeff Law]

https://gcc.gnu.org/g:1a2b5eeb5d24a44db9cb757906bd06912af15379

commit r16-6485-g1a2b5eeb5d24a44db9cb757906bd06912af15379
Author: Kalvis Duckmanton <kalvisd@gmail.com>
Date:   Sun Jan 4 10:54:48 2026 -0700

    [PATCH v2]: pch, target: update host hooks for NetBSD and OpenBSD
    
    The PCH use_address hooks for NetBSD hosts have not yet been updated to allow
    compiled headers to be loaded at an address different from their preferred
    address.
    
    This change updates host-netbsd.cc:netbsd_gt_pch_use_address() thus: if a
    compiled header cannot be mapped at its preferred address, a region of memory
    is allocated and the base address of this region is passed back to the caller
    (ggc-common.cc:gt_pch_restore() I believe).  Note that in this case the return
    value is 0, allowing gt_pch_restore() to load the header.  In this respect the
    behaviour is slightly different from that of the use_address hook for other
    hosts (e.g. Linux).
    
    This change against GCC 15.2.0 builds on the work in pch/71934 (and
    target/58937)
    
    gcc/
            * config/host-netbsd.cc (netbsd_gt_pch_use_address): Support PCH
            loading at addresses other than its preferred address.
            * config/host-openbsd.cc (openbsd_gt_pch_use_address): Likewise.

Diff:
---
 gcc/config/host-netbsd.cc  | 16 +++++++++++++++-
 gcc/config/host-openbsd.cc | 16 +++++++++++++++-
 2 files changed, 30 insertions(+), 2 deletions(-)

diff --git a/gcc/config/host-netbsd.cc b/gcc/config/host-netbsd.cc
index a6f12d0ecf0d..a5b449944939 100644
--- a/gcc/config/host-netbsd.cc
+++ b/gcc/config/host-netbsd.cc
@@ -78,7 +78,21 @@ netbsd_gt_pch_use_address (void *&base, size_t size, int fd, size_t offset)
 
   addr = mmap (base, size, PROT_READ | PROT_WRITE, MAP_PRIVATE | MAP_FIXED, fd, offset);
 
-  return addr == base ? 1 : -1;
+  if (addr == base)
+    return 1;
+
+  if (addr != (void *) MAP_FAILED)
+    munmap(addr, size);
+
+  addr = mmap (base, size, PROT_READ | PROT_WRITE, MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
+
+  if (addr == (void *) MAP_FAILED)
+    return -1;
+
+  /* Signal to the caller that whilst memory has been allocated, it
+     must read the PCH data */
+  base = addr;
+  return 0;
 }
 
 
diff --git a/gcc/config/host-openbsd.cc b/gcc/config/host-openbsd.cc
index ee09df361820..ac5f913ed914 100644
--- a/gcc/config/host-openbsd.cc
+++ b/gcc/config/host-openbsd.cc
@@ -78,7 +78,21 @@ openbsd_gt_pch_use_address (void *&base, size_t size, int fd, size_t offset)
 
   addr = mmap (base, size, PROT_READ | PROT_WRITE, MAP_PRIVATE, fd, offset);
 
-  return addr == base ? 1 : -1;
+  if (addr == base)
+    return 1;
+
+  if (addr != (void *) MAP_FAILED)
+    munmap(addr, size);
+
+  addr = mmap (base, size, PROT_READ | PROT_WRITE, MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
+
+  if (addr == (void *) MAP_FAILED)
+    return -1;
+
+  /* Signal to the caller that whilst memory has been allocated, it
+     must read the PCH data */
+  base = addr;
+  return 0;
 }