build: Disable Visual Studio warning "conditional expression is constant"

- Disable warning C4127 "conditional expression is constant" globally
  in curl_setup.h for when building with Microsoft's compiler.

This mainly affects building with the Visual Studio project files found
in the projects dir.

Prior to this change the cmake and winbuild build systems already
disabled 4127 globally for when building with Microsoft's compiler.
Also, 4127 was already disabled for all build systems in the limited
circumstance of the WHILE_FALSE macro which disabled the warning
specifically for while(0). This commit removes the WHILE_FALSE macro and
all other cruft in favor of disabling globally in curl_setup.

Background:

We have various macros that cause 0 or 1 to be evaluated, which would
cause warning C4127 in Visual Studio. For example this causes it:

    #define Curl_resolver_asynch() 1

Full behavior is not clearly defined and inconsistent across versions.
However it is documented that since VS 2015 Update 3 Microsoft has
addressed this somewhat but not entirely, not warning on while(true) for
example.

Prior to this change some C4127 warnings occurred when I built with
Visual Studio using the generated projects in the projects dir.

Closes https://github.com/curl/curl/pull/4658

lib/CMakeLists.txt

@@ -20,7 +20,6 @@ list(APPEND HHEADERS
 
 if(MSVC)
   list(APPEND CSOURCES libcurl.rc)
-  set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} /wd4127")
 endif()
 
 # SET(CSOURCES

lib/cookie.c

@@ -1227,7 +1227,7 @@ static int cookie_sort_ct(const void *p1, const void *p2)
       if(!d->field)                      \
         goto fail;                       \
     }                                    \
-  } WHILE_FALSE
+  } while(0)
 
 static struct Cookie *dup_cookie(struct Cookie *src)
 {

lib/curl_multibyte.h

@@ -62,7 +62,7 @@ char *Curl_convert_wchar_to_UTF8(const wchar_t *str_w);
 #define Curl_convert_UTF8_to_tchar(ptr) Curl_convert_UTF8_to_wchar((ptr))
 #define Curl_convert_tchar_to_UTF8(ptr) Curl_convert_wchar_to_UTF8((ptr))
 #define Curl_unicodefree(ptr) \
-  do {if((ptr)) {free((ptr)); (ptr) = NULL;}} WHILE_FALSE
+  do {if((ptr)) {free((ptr)); (ptr) = NULL;}} while(0)
 
 typedef union {
   unsigned short       *tchar_ptr;
@@ -76,7 +76,7 @@ typedef union {
 #define Curl_convert_UTF8_to_tchar(ptr) (ptr)
 #define Curl_convert_tchar_to_UTF8(ptr) (ptr)
 #define Curl_unicodefree(ptr) \
-  do {(ptr) = NULL;} WHILE_FALSE
+  do {(ptr) = NULL;} while(0)
 
 typedef union {
   char                *tchar_ptr;

lib/curl_setup.h

@@ -26,6 +26,14 @@
 #define CURL_NO_OLDIES
 #endif
 
+/*
+ * Disable Visual Studio warnings:
+ * 4127 "conditional expression is constant"
+ */
+#ifdef _MSC_VER
+#pragma warning(disable:4127)
+#endif
+
 /*
  * Define WIN32 when build target is Win32 API
  */
@@ -714,7 +722,7 @@ int netware_init(void);
  */
 
 #ifndef Curl_nop_stmt
-#  define Curl_nop_stmt do { } WHILE_FALSE
+#  define Curl_nop_stmt do { } while(0)
 #endif
 
 /*

lib/curl_setup_once.h

@@ -329,27 +329,6 @@ struct timeval {
 
 #include "curl_ctype.h"
 
-/*
- * Macro WHILE_FALSE may be used to build single-iteration do-while loops,
- * avoiding compiler warnings. Mostly intended for other macro definitions.
- */
-
-#define WHILE_FALSE  while(0)
-
-#if defined(_MSC_VER) && !defined(__POCC__)
-#  undef WHILE_FALSE
-#  if (_MSC_VER < 1500)
-#    define WHILE_FALSE  while(1, 0)
-#  else
-#    define WHILE_FALSE \
-__pragma(warning(push)) \
-__pragma(warning(disable:4127)) \
-while(0) \
-__pragma(warning(pop))
-#  endif
-#endif
-
-
 /*
  * Typedef to 'int' if sig_atomic_t is not an available 'typedefed' type.
  */
@@ -387,7 +366,7 @@ typedef int sig_atomic_t;
 #ifdef DEBUGBUILD
 #define DEBUGF(x) x
 #else
-#define DEBUGF(x) do { } WHILE_FALSE
+#define DEBUGF(x) do { } while(0)
 #endif
 
 
@@ -398,7 +377,7 @@ typedef int sig_atomic_t;
 #if defined(DEBUGBUILD) && defined(HAVE_ASSERT_H)
 #define DEBUGASSERT(x) assert(x)
 #else
-#define DEBUGASSERT(x) do { } WHILE_FALSE
+#define DEBUGASSERT(x) do { } while(0)
 #endif
 
 

lib/doh.c

@@ -218,7 +218,7 @@ do {                                      \
   result = curl_easy_setopt(doh, x, y);   \
   if(result)                              \
     goto error;                           \
-} WHILE_FALSE
+} while(0)
 
 static CURLcode dohprobe(struct Curl_easy *data,
                          struct dnsprobe *p, DNStype dnstype,

lib/http2.c

@@ -68,7 +68,7 @@
 #ifdef DEBUG_HTTP2
 #define H2BUGF(x) x
 #else
-#define H2BUGF(x) do { } WHILE_FALSE
+#define H2BUGF(x) do { } while(0)
 #endif
 
 

lib/ldap.c

@@ -112,7 +112,7 @@ static void _ldap_free_urldesc(LDAPURLDesc *ludp);
   #define LDAP_TRACE(x)   do { \
                             _ldap_trace("%u: ", __LINE__); \
                             _ldap_trace x; \
-                          } WHILE_FALSE
+                          } while(0)
 
   static void _ldap_trace(const char *fmt, ...);
 #else

lib/memdebug.h

@@ -169,6 +169,6 @@ CURL_EXTERN int curl_dbg_fclose(FILE *file, int line, const char *source);
  */
 
 #define Curl_safefree(ptr) \
-  do { free((ptr)); (ptr) = NULL;} WHILE_FALSE
+  do { free((ptr)); (ptr) = NULL;} while(0)
 
 #endif /* HEADER_CURL_MEMDEBUG_H */

lib/mprintf.c

@@ -104,7 +104,7 @@ static const char upper_digits[] = "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ";
       done++; \
     else \
      return done; /* return immediately on failure */ \
-  } WHILE_FALSE
+  } while(0)
 
 /* Data type to read from the arglist */
 typedef enum {

lib/select.h

@@ -109,7 +109,7 @@ int tpf_select_libcurl(int maxfds, fd_set* reads, fd_set* writes,
     SET_SOCKERRNO(EINVAL); \
     return -1; \
   } \
-} WHILE_FALSE
+} while(0)
 #endif
 
 #endif /* HEADER_CURL_SELECT_H */

lib/sendf.c

@@ -224,7 +224,7 @@ bool Curl_recv_has_postponed_data(struct connectdata *conn, int sockindex)
   (void)sockindex;
   return false;
 }
-#define pre_receive_plain(c,n) do {} WHILE_FALSE
+#define pre_receive_plain(c,n) do {} while(0)
 #define get_pre_recved(c,n,b,l) 0
 #endif /* ! USE_RECV_BEFORE_SEND_WORKAROUND */
 

lib/sha256.c

@@ -58,7 +58,7 @@ do {                                                                \
   (a)[1] = (unsigned char)((((unsigned long) (val)) >> 16) & 0xff); \
   (a)[2] = (unsigned char)((((unsigned long) (val)) >> 8) & 0xff);  \
   (a)[3] = (unsigned char)(((unsigned long) (val)) & 0xff);         \
-} WHILE_FALSE;
+} while(0)
 
 #ifdef HAVE_LONGLONG
 #define WPA_PUT_BE64(a, val)                                    \
@@ -71,7 +71,7 @@ do {                                                            \
   (a)[5] = (unsigned char)(((unsigned long long)(val)) >> 16);  \
   (a)[6] = (unsigned char)(((unsigned long long)(val)) >> 8);   \
   (a)[7] = (unsigned char)(((unsigned long long)(val)) & 0xff); \
-} WHILE_FALSE;
+} while(0)
 #else
 #define WPA_PUT_BE64(a, val)                                  \
 do {                                                          \

lib/telnet.c

@@ -69,12 +69,12 @@
   do {                                                  \
     x->subend = x->subpointer;                          \
     CURL_SB_CLEAR(x);                                   \
-  } WHILE_FALSE
+  } while(0)
 #define CURL_SB_ACCUM(x,c)                                      \
   do {                                                          \
     if(x->subpointer < (x->subbuffer + sizeof(x->subbuffer)))   \
       *x->subpointer++ = (c);                                   \
-  } WHILE_FALSE
+  } while(0)
 
 #define  CURL_SB_GET(x) ((*x->subpointer++)&0xff)
 #define  CURL_SB_LEN(x) (x->subend - x->subpointer)

lib/transfer.c

@@ -1177,7 +1177,7 @@ static CURLcode readwrite_upload(struct Curl_easy *data,
     }
 
 
-  } WHILE_FALSE; /* just to break out from! */
+  } while(0); /* just to break out from! */
 
   return CURLE_OK;
 }

lib/url.c

@@ -674,7 +674,7 @@ static void conn_reset_all_postponed_data(struct connectdata *conn)
 }
 #else  /* ! USE_RECV_BEFORE_SEND_WORKAROUND */
 /* Use "do-nothing" macro instead of function when workaround not used */
-#define conn_reset_all_postponed_data(c) do {} WHILE_FALSE
+#define conn_reset_all_postponed_data(c) do {} while(0)
 #endif /* ! USE_RECV_BEFORE_SEND_WORKAROUND */
 
 

lib/vquic/ngtcp2.c

@@ -49,7 +49,7 @@
 #ifdef DEBUG_HTTP3
 #define H3BUGF(x) x
 #else
-#define H3BUGF(x) do { } WHILE_FALSE
+#define H3BUGF(x) do { } while(0)
 #endif
 
 /*

lib/vquic/quiche.c

@@ -45,7 +45,7 @@
 #ifdef DEBUG_HTTP3
 #define H3BUGF(x) x
 #else
-#define H3BUGF(x) do { } WHILE_FALSE
+#define H3BUGF(x) do { } while(0)
 #endif
 
 #define QUIC_MAX_STREAMS (256*1024)

lib/vssh/libssh.c

@@ -98,7 +98,7 @@
 /* A recent macro provided by libssh. Or make our own. */
 #ifndef SSH_STRING_FREE_CHAR
 #define SSH_STRING_FREE_CHAR(x) \
-    do { if((x) != NULL) { ssh_string_free_char(x); x = NULL; } } WHILE_FALSE
+    do { if((x) != NULL) { ssh_string_free_char(x); x = NULL; } } while(0)
 #endif
 
 /* Local functions: */

lib/vtls/nss.c

@@ -113,7 +113,7 @@ typedef struct {
   ptr->type = (_type);                                      \
   ptr->pValue = (_val);                                     \
   ptr->ulValueLen = (_len);                                 \
-} WHILE_FALSE
+} while(0)
 
 #define CERT_NewTempCertificate __CERT_NewTempCertificate
 

lib/vtls/openssl.c

@@ -3077,7 +3077,7 @@ do {                              \
   Curl_ssl_push_certinfo_len(data, _num, _label, ptr, info_len); \
   if(1 != BIO_reset(mem))                                        \
     break;                                                       \
-} WHILE_FALSE
+} while(0)
 
 static void pubkey_show(struct Curl_easy *data,
                         BIO *mem,
@@ -3109,7 +3109,7 @@ do {                              \
   if(_type->_name) { \
     pubkey_show(data, mem, _num, #_type, #_name, _type->_name); \
   } \
-} WHILE_FALSE
+} while(0)
 #endif
 
 static int X509V3_ext(struct Curl_easy *data,