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feat: opt-in ASYNCWEBSERVER_USE_PSRAM - allocate handler objects in PSRAM (ESP32) #468

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feat: opt-in ASYNCWEBSERVER_USE_PSRAM - allocate handler objects in PSRAM (ESP32) #468

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24 changes: 24 additions & 0 deletions src/ESPAsyncWebServer.h
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Original file line number Diff line number Diff line change
Expand Up @@ -10,6 +10,10 @@
#include <lwip/tcpbase.h>
#endif

#if defined(ESP32) && defined(ASYNCWEBSERVER_USE_PSRAM)
#include <esp_heap_caps.h>
#endif

#include <algorithm>
#include <deque>
#include <functional>
Expand Down Expand Up @@ -1528,6 +1532,26 @@ class AsyncWebHandler : public AsyncMiddlewareChain {
public:
AsyncWebHandler() {}
virtual ~AsyncWebHandler() {}
#if defined(ESP32) && defined(ASYNCWEBSERVER_USE_PSRAM)
// Opt-in (-D ASYNCWEBSERVER_USE_PSRAM): allocate handler objects in PSRAM
// to preserve scarce internal SRAM. All handlers derive from this base
// (route handlers, catch-all, AsyncWebSocket, static file handlers), they
// are created after PSRAM is initialized and are only read during request
// dispatch - never from an ISR or DMA context - so external RAM is safe
// and the added latency is irrelevant. Falls back to the internal heap
// when PSRAM is absent or exhausted, so the flag is safe to set on
// targets without PSRAM as well.
void *operator new(size_t size) {
void *p = heap_caps_malloc(size, MALLOC_CAP_SPIRAM);
if (!p) {
p = malloc(size);
}
return p;

@mathieucarbou mathieucarbou Jul 28, 2026

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I think that if new fails on ESP32 it does throw std::bad_alloc (which crashes the esp). Here it would return null right ?

@willmmiles willmmiles Jul 28, 2026

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Correct, operator new(size_t) is required to throw std::bad_alloc on an allocation failure. operator new(size_t, const std::nothrow&) is the variant that returns null.

}
void operator delete(void *ptr) {
heap_caps_free(ptr); // valid for both PSRAM and internal allocations
}
#endif
AsyncWebHandler &setFilter(ArRequestFilterFunction fn);
AsyncWebHandler &setAuthentication(const char *username, const char *password, AsyncAuthType authMethod = AsyncAuthType::AUTH_DIGEST);
AsyncWebHandler &setAuthentication(const String &username, const String &password, AsyncAuthType authMethod = AsyncAuthType::AUTH_DIGEST) {
Expand Down