[gcc r17-4105] gccrs: Fix sized BIR IndexVec construction

[Arthur Cohen via Gcc-cvs]

https://gcc.gnu.org/g:725f4e741e13be79bc1c6684346ec16f522d8a76

commit r17-4105-g725f4e741e13be79bc1c6684346ec16f522d8a76
Author: Lishin <lishin1...@gmail.com>
Date:   Sat Jul 25 14:31:42 2026 +0000

    gccrs: Fix sized BIR IndexVec construction
    
    Create the requested number of elements in the IndexVec constructor
    instead of only reserving space. This fixes an out-of-bounds access
    when dumping BIR.
    
    gcc/rust/ChangeLog:
    
            * checks/errors/borrowck/rust-bir-place.h
            (IndexVec::IndexVec): Create the requested number of elements.
    
    Signed-off-by: Lishin <lishin1...@gmail.com>

Diff:
---
 gcc/rust/checks/errors/borrowck/rust-bir-place.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/gcc/rust/checks/errors/borrowck/rust-bir-place.h 
b/gcc/rust/checks/errors/borrowck/rust-bir-place.h
index e7a31b9df6dc..d11ded9c9daa 100644
--- a/gcc/rust/checks/errors/borrowck/rust-bir-place.h
+++ b/gcc/rust/checks/errors/borrowck/rust-bir-place.h
@@ -209,7 +209,7 @@ template <typename I, typename T> class IndexVec
 
 public:
   IndexVec () = default;
-  IndexVec (size_t size) { internal_vector.reserve (size); }
+  IndexVec (size_t size) : internal_vector (size) {}
 
   T &at (I pid) { return internal_vector[pid.value]; }
   const T &at (I pid) const { return internal_vector[pid.value]; }