Remove mInfo field from Cancelable by default. (project-chip#29262)

* Remove mInfo field from Cancelable by default. It's big, and totally unused. The opt-in to enable it is for backwards compat. If we care about preserving compat while also ensuring that some internal Cancelable uses never have this field, that is also possible, but more complicated. * Apply suggestion from code review. Co-authored-by: Tennessee Carmel-Veilleux <tennessee.carmelveilleux@gmail.com> --------- Co-authored-by: Tennessee Carmel-Veilleux <tennessee.carmelveilleux@gmail.com>
HunsupJung · Oct 23, 2023 · 89d3ca2 · 89d3ca2
1 parent f5441fe
commit 89d3ca2
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Showing 3 changed files with 13 additions and 0 deletions.
diff --git a/src/lib/core/BUILD.gn b/src/lib/core/BUILD.gn
@@ -64,6 +64,7 @@ buildconfig_header("chip_buildconfig") {
     "CHIP_CONFIG_TRANSPORT_PW_TRACE_ENABLED=${chip_enable_transport_pw_trace}",
     "CHIP_CONFIG_MINMDNS_DYNAMIC_OPERATIONAL_RESPONDER_LIST=${chip_config_minmdns_dynamic_operational_responder_list}",
     "CHIP_CONFIG_MINMDNS_MAX_PARALLEL_RESOLVES=${chip_config_minmdns_max_parallel_resolves}",
+    "CHIP_CONFIG_CANCELABLE_HAS_INFO_STRING_FIELD=${chip_config_cancelable_has_info_string_field}",
   ]
 }
 

diff --git a/src/lib/core/CHIPCallback.h b/src/lib/core/CHIPCallback.h
@@ -26,6 +26,8 @@
 #include <stddef.h>
 #include <stdint.h>
 
+#include <lib/core/CHIPConfig.h>
+
 namespace chip {
 
 namespace Callback {
@@ -49,7 +51,13 @@ class Cancelable
      */
     Cancelable * mNext;
     Cancelable * mPrev;
+
+    // CHIP_CONFIG_CANCELABLE_HAS_INFO_STRING_FIELD allows consumers that were
+    // using this field to opt into having it (and the resulting memory bloat)
+    // while allowing everyone else to save the memory.
+#if CHIP_CONFIG_CANCELABLE_HAS_INFO_STRING_FIELD
     alignas(uint64_t) char mInfo[24];
+#endif // CHIP_CONFIG_CANCELABLE_HAS_INFO_STRING_FIELD
 
     /**
      * @brief when non-null, indicates the Callback is registered with

diff --git a/src/lib/core/core.gni b/src/lib/core/core.gni
@@ -84,6 +84,10 @@ declare_args() {
 
   # When using minmdns, set the number of parallel resolves
   chip_config_minmdns_max_parallel_resolves = 2
+
+  # If set to true, adds a string "info" field to Cancelable.
+  # Only here for backwards compat.  Generally, THIS SHOULD NOT BE SET TO TRUE.
+  chip_config_cancelable_has_info_string_field = false
 }
 
 if (chip_target_style == "") {