Improve macro hygiene

This commit improves hygiene and formatting of macro definitions
throughout the library. Specifically:
- It adds brackets around parameters to avoid unintended
  interpretation of arguments, e.g. due to operator precedence.
- It adds uses of the `do { ... } while( 0 )` idiom for macros that
  can be used as commands.

include/mbedtls/asn1write.h

@@ -33,11 +33,12 @@
 #include "asn1.h"
 
 #define MBEDTLS_ASN1_CHK_ADD(g, f)                      \
-    do {                                                \
-        if( ( ret = f ) < 0 )                           \
+    do                                                  \
+    {                                                   \
+        if( ( ret = (f) ) < 0 )                         \
             return( ret );                              \
         else                                            \
-            g += ret;                                   \
+            (g) += ret;                                 \
     } while( 0 )
 
 #ifdef __cplusplus

include/mbedtls/bignum.h

@@ -46,7 +46,12 @@
 #define MBEDTLS_ERR_MPI_NOT_ACCEPTABLE                    -0x000E  /**< The input arguments are not acceptable. */
 #define MBEDTLS_ERR_MPI_ALLOC_FAILED                      -0x0010  /**< Memory allocation failed. */
 
-#define MBEDTLS_MPI_CHK(f) do { if( ( ret = f ) != 0 ) goto cleanup; } while( 0 )
+#define MBEDTLS_MPI_CHK(f)       \
+    do                           \
+    {                            \
+        if( ( ret = (f) ) != 0 ) \
+            goto cleanup;        \
+    } while( 0 )
 
 /*
  * Maximum size MPIs are allowed to grow to in number of limbs.

include/mbedtls/padlock.h

@@ -59,7 +59,7 @@
 #define MBEDTLS_PADLOCK_PHE 0x0C00
 #define MBEDTLS_PADLOCK_PMM 0x3000
 
-#define MBEDTLS_PADLOCK_ALIGN16(x) (uint32_t *) (16 + ((int32_t) x & ~15))
+#define MBEDTLS_PADLOCK_ALIGN16(x) (uint32_t *) (16 + ((int32_t) (x) & ~15))
 
 #ifdef __cplusplus
 extern "C" {

include/mbedtls/x509_crt.h

@@ -98,7 +98,7 @@ mbedtls_x509_crt;
  * Build flag from an algorithm/curve identifier (pk, md, ecp)
  * Since 0 is always XXX_NONE, ignore it.
  */
-#define MBEDTLS_X509_ID_FLAG( id )   ( 1 << ( id - 1 ) )
+#define MBEDTLS_X509_ID_FLAG( id )   ( 1 << ( (id) - 1 ) )
 
 /**
  * Security profile for certificate verification.