Linux: Guard mallinfo() use behind check for __GLIBC__ (#33626)

* Linux: Guard mallinfo() use behind check for __GLIBC__

* Use positive checks for __GLIBC__ rather than ifndef

src/platform/Linux/DiagnosticDataProviderImpl.cpp

@@ -74,8 +74,10 @@ enum class WiFiStatsCountType
     kWiFiOverrunCount
 };
 
+#if defined(__GLIBC__)
 // Static variable to store the maximum heap size
 static size_t maxHeapHighWatermark = 0;
+#endif
 
 CHIP_ERROR GetEthernetStatsCount(EthernetStatsCountType type, uint64_t & count)
 {
@@ -223,24 +225,22 @@ DiagnosticDataProviderImpl & DiagnosticDataProviderImpl::GetDefaultInstance()
 
 CHIP_ERROR DiagnosticDataProviderImpl::GetCurrentHeapFree(uint64_t & currentHeapFree)
 {
-#ifndef __GLIBC__
-    return CHIP_ERROR_NOT_IMPLEMENTED;
-#else
+#if defined(__GLIBC__)
     struct mallinfo mallocInfo = mallinfo();
 
     // Get the current amount of heap memory, in bytes, that are not being utilized
     // by the current running program.
     currentHeapFree = mallocInfo.fordblks;
 
     return CHIP_NO_ERROR;
+#else
+    return CHIP_ERROR_NOT_IMPLEMENTED;
 #endif
 }
 
 CHIP_ERROR DiagnosticDataProviderImpl::GetCurrentHeapUsed(uint64_t & currentHeapUsed)
 {
-#ifndef __GLIBC__
-    return CHIP_ERROR_NOT_IMPLEMENTED;
-#else
+#if defined(__GLIBC__)
     struct mallinfo mallocInfo = mallinfo();
 
     // Get the current amount of heap memory, in bytes, that are being used by
@@ -253,14 +253,14 @@ CHIP_ERROR DiagnosticDataProviderImpl::GetCurrentHeapUsed(uint64_t & currentHeap
         maxHeapHighWatermark = currentHeapUsed;
     }
     return CHIP_NO_ERROR;
+#else
+    return CHIP_ERROR_NOT_IMPLEMENTED;
 #endif
 }
 
 CHIP_ERROR DiagnosticDataProviderImpl::GetCurrentHeapHighWatermark(uint64_t & currentHeapHighWatermark)
 {
-#ifndef __GLIBC__
-    return CHIP_ERROR_NOT_IMPLEMENTED;
-#else
+#if defined(__GLIBC__)
     struct mallinfo mallocInfo = mallinfo();
 
     // The usecase of this function is embedded devices,on which we would need to intercept
@@ -279,6 +279,8 @@ CHIP_ERROR DiagnosticDataProviderImpl::GetCurrentHeapHighWatermark(uint64_t & cu
     currentHeapHighWatermark = maxHeapHighWatermark;
 
     return CHIP_NO_ERROR;
+#else
+    return CHIP_ERROR_NOT_IMPLEMENTED;
 #endif
 }
 
@@ -287,10 +289,12 @@ CHIP_ERROR DiagnosticDataProviderImpl::ResetWatermarks()
     // If implemented, the server SHALL set the value of the CurrentHeapHighWatermark attribute to the
     // value of the CurrentHeapUsed.
 
+#if defined(__GLIBC__)
     // Get the current amount of heap memory, in bytes, that are being used by
     // the current running program and reset the max heap high watermark to current heap amount.
     struct mallinfo mallocInfo = mallinfo();
     maxHeapHighWatermark       = mallocInfo.uordblks;
+#endif
 
     return CHIP_NO_ERROR;
 }