[libc] Cleanup startup/baremetal/arm/start.cpp (#151532)

Post-commit review changes as suggested by @petrhosek in #146863

Author: saturn691

libc/startup/baremetal/arm/start.cpp

@@ -6,6 +6,7 @@
 //
 //===----------------------------------------------------------------------===//
 
+#include "hdr/stdint_proxy.h"
 #include "src/__support/macros/config.h"
 #include "src/stdlib/atexit.h"
 #include "src/stdlib/exit.h"
@@ -14,8 +15,6 @@
 #include "startup/baremetal/fini.h"
 #include "startup/baremetal/init.h"
 
-#include <stdint.h>
-
 extern "C" {
 int main(int argc, char **argv);
 void _start();
@@ -31,7 +30,9 @@ extern uintptr_t __data_start[];
 extern uintptr_t __data_size[];
 extern uintptr_t __bss_start[];
 extern uintptr_t __bss_size[];
+} // extern "C"
 
+namespace {
 // Based on
 // https://developer.arm.com/documentation/107565/0101/Use-case-examples/Generic-Information/What-is-inside-a-program-image-/Vector-table
 void NMI_Handler() {}
@@ -49,35 +50,37 @@ void SysTick_Handler() {}
 // to be zero and Cortex-M23 can require up to 10, so 1024-byte align the vector
 // table.
 using HandlerType = void (*)(void);
-const HandlerType vector_table[]
-    __attribute__((section(".vectors"), aligned(1024), used)) = {
-        (HandlerType)&__stack, // SP
-        _start,                // Reset
-        NMI_Handler,           // NMI Handler
-        HardFault_Handler,     // Hard Fault Handlerß
-        MemManage_Handler,     // MPU Fault Han`dler
-        BusFault_Handler,      // Bus Fault Handler
-        UsageFault_Handler,    // Usage Fault Handler
-        0,                     // Reserved
-        0,                     // Reserved
-        0,                     // Reserved
-        0,                     // Reserved
-        SVC_Handler,           // SVC Handler
-        DebugMon_Handler,      // Debug Monitor Handler
-        0,                     // Reserved
-        PendSV_Handler,        // PendSV Handler
-        SysTick_Handler,       // SysTick Handler
-                               // Unused
+[[gnu::section(".vectors"), gnu::aligned(1024), gnu::used]]
+const HandlerType vector_table[] = {
+    reinterpret_cast<HandlerType>(&__stack), // SP
+    _start,                                  // Reset
+    NMI_Handler,                             // NMI Handler
+    HardFault_Handler,                       // Hard Fault Handlerß
+    MemManage_Handler,                       // MPU Fault Han`dler
+    BusFault_Handler,                        // Bus Fault Handler
+    UsageFault_Handler,                      // Usage Fault Handler
+    0,                                       // Reserved
+    0,                                       // Reserved
+    0,                                       // Reserved
+    0,                                       // Reserved
+    SVC_Handler,                             // SVC Handler
+    DebugMon_Handler,                        // Debug Monitor Handler
+    0,                                       // Reserved
+    PendSV_Handler,                          // PendSV Handler
+    SysTick_Handler,                         // SysTick Handler
+                                             // Unused
 };
-} // extern "C"
+} // namespace
 
 namespace LIBC_NAMESPACE_DECL {
 [[noreturn]] void do_start() {
   // FIXME: set up the QEMU test environment
 
   // Perform the equivalent of scatterloading
-  LIBC_NAMESPACE::memcpy(__data_start, __data_source, (uintptr_t)__data_size);
-  LIBC_NAMESPACE::memset(__bss_start, '\0', (uintptr_t)__bss_size);
+  LIBC_NAMESPACE::memcpy(__data_start, __data_source,
+                         reinterpret_cast<uintptr_t>(__data_size));
+  LIBC_NAMESPACE::memset(__bss_start, '\0',
+                         reinterpret_cast<uintptr_t>(__bss_size));
   __libc_init_array();
 
   _platform_init();