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new c36d99a560 GCC 15: Address mismatched-new-delete in MemArena::Block
(#12163)
c36d99a560 is described below
commit c36d99a56047b4a96e66e1bcd54a2891a4f23297
Author: Brian Neradt <brian.ner...@gmail.com>
AuthorDate: Fri Apr 4 15:43:38 2025 -0500
GCC 15: Address mismatched-new-delete in MemArena::Block (#12163)
This addresses a GCC 15 compiler warning about mismatched std operator
new and overridden operator delete in MemArena. This patch addresses the
warning by also overriding operator new for the MemArena::Block.
This is the warning being addressed:
```
lib/swoc/src/MemArena.cc: In member function
‘swoc::_1_5_14::MemArena::Block* swoc::_1_5_14::MemArena::make_block(size_t)’:
lib/swoc/src/MemArena.cc:99:44: error: ‘static void
swoc::_1_5_14::MemArena::Block::operator delete(void*, void*)’ called on
pointer returned from a mismatched allocation function [-Werror=mism
atched-new-delete]
99 | return new (::malloc(n)) Block(free_space);
| ^
src/ts_asf_master_fix_builds_for_fedora_42/lib/swoc/src/MemArena.cc:99:23:
note: returned from ‘void* malloc(size_t)’
99 | return new (::malloc(n)) Block(free_space);
| ~~~~~~~~^~~
```
---
lib/swoc/include/swoc/MemArena.h | 40 ++++++++++++++++++++++++++++++++++++++++
lib/swoc/src/MemArena.cc | 6 ++----
2 files changed, 42 insertions(+), 4 deletions(-)
diff --git a/lib/swoc/include/swoc/MemArena.h b/lib/swoc/include/swoc/MemArena.h
index e0b25fb2e1..f9605993d2 100644
--- a/lib/swoc/include/swoc/MemArena.h
+++ b/lib/swoc/include/swoc/MemArena.h
@@ -9,6 +9,8 @@
#include <mutex>
#include <memory>
+#include <stdexcept>
+#include <type_traits>
#include <utility>
#include <new>
#if __has_include(<memory_resource>)
@@ -124,6 +126,24 @@ public:
protected:
friend MemArena; ///< Container.
+ /** A custom @c operator @c new.
+ *
+ * Compilers complain about mismatched std operator new and the custom
+ * operator delete unless this custom operator new is provided.
+ *
+ * @param block_size The implicit compiler-provided sizeof(Block), the
object size.
+ * @param n The number of bytes the user is requesting for the backend
storage of Block.
+ * @return Pointer to the allocated memory.
+ */
+ static void* operator new(size_t block_size, size_t n);
+
+ /** Override placement (non-allocated) @c new.
+ * @param block_size The implicit compiler-provided sizeof(Block), the
object size. Not used.
+ * @param place Value passed to @c new.
+ * @return Pointer to the memory.
+ */
+ static void* operator new([[maybe_unused]] size_t block_size, void* place)
noexcept;
+
/** Override @c operator @c delete.
*
* This is required because the allocated memory size is larger than the
class size which
@@ -641,6 +661,26 @@ MemArena::Block::discard() {
return *this;
}
+inline void*
+MemArena::Block::operator new(size_t block_size, size_t n)
+{
+ if (n < block_size) {
+ throw std::invalid_argument("MemArena::Block::operator new size is less
than object size.");
+ }
+ // In theory we could use ::operator new(n) but this causes a size mismatch
during ::operator delete.
+ // Easier to use malloc here and also override @c delete.
+ auto b = static_cast<Block *>(::malloc(n));
+ if (b == nullptr) {
+ throw std::bad_alloc();
+ }
+ return b;
+}
+
+inline void*
+MemArena::Block::operator new([[maybe_unused]] size_t block_size, void* place)
noexcept {
+ return place;
+}
+
inline void
MemArena::Block::operator delete(void *ptr) noexcept {
::free(ptr);
diff --git a/lib/swoc/src/MemArena.cc b/lib/swoc/src/MemArena.cc
index 1d4d708ca3..8621467994 100644
--- a/lib/swoc/src/MemArena.cc
+++ b/lib/swoc/src/MemArena.cc
@@ -91,12 +91,10 @@ MemArena::make_block(size_t n) {
n = QuarterPage{round_up(n)};
}
- // Allocate space for the Block instance and the request memory and
construct a Block at the front.
- // In theory this could use ::operator new(n) but this causes a size
mismatch during ::operator delete.
- // Easier to use malloc and override @c delete.
+ // Allocate space for the Block instance and the requested memory and
construct a Block at the front.
auto free_space = n - sizeof(Block);
_active_reserved += free_space;
- return new (::malloc(n)) Block(free_space);
+ return new (n) Block(free_space);
}
MemSpan<void>
