musl: allocator: Fix __THROW and mallinfo

src/base/allocator/partition_allocator/src/partition_alloc/shim/allocator_shim_default_dispatch_to_partition_alloc.cc

@@ -1250,7 +1250,9 @@ SHIM_ALWAYS_EXPORT int mallopt(int cmd, int value) __THROW {
 
 #endif  // !PA_BUILDFLAG(IS_APPLE) && !PA_BUILDFLAG(IS_ANDROID)
 
-#if PA_BUILDFLAG(IS_LINUX) || PA_BUILDFLAG(IS_CHROMEOS)
+#if defined(__MUSL__)
+// Musl does not support struct mallinfo.
+#elif PA_BUILDFLAG(IS_LINUX) || PA_BUILDFLAG(IS_CHROMEOS)
 SHIM_ALWAYS_EXPORT struct mallinfo mallinfo(void) __THROW {
   partition_alloc::SimplePartitionStatsDumper allocator_dumper;
   // TODO(crbug.com/477186304): Dump stats for all alloc tokens, by accumulating

src/base/allocator/partition_allocator/src/partition_alloc/shim/allocator_shim_internals.h

@@ -10,7 +10,9 @@
 
 #if defined(__GNUC__)
 
-#if PA_BUILDFLAG(IS_POSIX)
+#if defined(__MUSL__)
+// Musl does not provide sys/cdefs.h
+#elif PA_BUILDFLAG(IS_POSIX)
 #include <sys/cdefs.h>  // for __THROW
 #endif
 

src/base/allocator/partition_allocator/src/partition_alloc/shim/allocator_shim_override_libc_symbols.h

@@ -25,6 +25,12 @@
 
 #include "partition_alloc/shim/allocator_shim_internals.h"
 
+// Musl does not specify anything for malloc() etc.
+#if defined(__MUSL__)
+#undef __THROW
+#define __THROW
+#endif
+
 extern "C" {
 
 // WARNING: Whenever a new function is added there (which, surprisingly enough,