[PATCH v2] RISC-V: Fix the warning of temporary object dangling references.

[Dongyan Chen]

During the GCC compilation, some warnings about temporary object dangling 
references emerged. They appeared in these code lines in riscv-common.cc:
const riscv_ext_info_t &implied_ext_info, const riscv_ext_info_t &ext_info = 
get_riscv_ext_info (ext) and auto &ext_info = get_riscv_ext_info (search_ext).
The issue arose because the local variable types were not used in a 
standardized way, causing their references to dangle once the function ended.
To fix this, the patch changes the argument type of get_riscv_ext_info to 
`const char *`, thereby eliminating the warnings.

Changes for v2:
- Change the argument type of get_riscv_ext_info to `const char *` to eliminate 
the warnings.

gcc/ChangeLog:

        * common/config/riscv/riscv-common.cc (get_riscv_ext_info): Fix 
argument type.
        (riscv_subset_list::check_implied_ext): Type conversion.

---
 gcc/common/config/riscv/riscv-common.cc | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/gcc/common/config/riscv/riscv-common.cc 
b/gcc/common/config/riscv/riscv-common.cc
index 53ca03910b38..c843393998cb 100644
--- a/gcc/common/config/riscv/riscv-common.cc
+++ b/gcc/common/config/riscv/riscv-common.cc
@@ -215,7 +215,7 @@ static const std::unordered_map<std::string, 
riscv_ext_info_t> riscv_ext_infos
 };

 static const riscv_ext_info_t &
-get_riscv_ext_info (const std::string &ext)
+get_riscv_ext_info (const char * ext)
 {
   auto itr = riscv_ext_infos.find (ext);
   if (itr == riscv_ext_infos.end ())
@@ -1112,7 +1112,7 @@ riscv_subset_list::check_implied_ext ()
   for (itr = m_head; itr != NULL; itr = itr->next)
     {
       auto &ext = *itr;
-      auto &ext_info = get_riscv_ext_info (ext.name);
+      auto &ext_info = get_riscv_ext_info (ext.name.c_str ());
       for (auto &implied_ext : ext_info.implied_exts ())
        {
          if (!implied_ext.match (this))
--
2.43.0