version: make curl_version* thread-safe without using global context

Closes #5010

lib/easy.c

@@ -83,8 +83,6 @@
 #include "curl_memory.h"
 #include "memdebug.h"
 
-void Curl_version_init(void);
-
 /* true globals -- for curl_global_init() and curl_global_cleanup() */
 static unsigned int  initialized;
 static long          init_flags;
@@ -201,8 +199,6 @@ static CURLcode global_init(long flags, bool memoryfuncs)
 
   init_flags = flags;
 
-  Curl_version_init();
-
   return CURLE_OK;
 
   fail:

lib/http2.c

@@ -333,7 +333,7 @@ static const struct Curl_handler Curl_handler_http2_ssl = {
 int Curl_http2_ver(char *p, size_t len)
 {
   nghttp2_info *h2 = nghttp2_version(0);
-  return msnprintf(p, len, " nghttp2/%s", h2->version_str);
+  return msnprintf(p, len, "nghttp2/%s", h2->version_str);
 }
 
 /*

lib/version.c

@@ -66,16 +66,6 @@
 #include <brotli/decode.h>
 #endif
 
-void Curl_version_init(void);
-
-/* For thread safety purposes this function is called by global_init so that
-   the static data in both version functions is initialized. */
-void Curl_version_init(void)
-{
-  curl_version();
-  curl_version_info(CURLVERSION_NOW);
-}
-
 #ifdef HAVE_BROTLI
 static size_t brotli_version(char *buf, size_t bufsz)
 {
@@ -88,95 +78,108 @@ static size_t brotli_version(char *buf, size_t bufsz)
 }
 #endif
 
+/*
+ * curl_version() returns a pointer to a static buffer.
+ *
+ * It is implemented to work multi-threaded by making sure repeated invokes
+ * generate the exact same string and never write any temporary data like
+ * zeros in the data.
+ */
 char *curl_version(void)
 {
-  static bool initialized;
-  static char version[250];
-  char *ptr = version;
-  size_t len;
-  size_t left = sizeof(version);
-
-  if(initialized)
-    return version;
-
-  strcpy(ptr, LIBCURL_NAME "/" LIBCURL_VERSION);
-  len = strlen(ptr);
-  left -= len;
-  ptr += len;
-
-  len = Curl_ssl_version(ptr + 1, left - 1);
-
-  if(len > 0) {
-    *ptr = ' ';
-    left -= ++len;
-    ptr += len;
-  }
-
+  static char out[250];
+  char *outp;
+  size_t outlen;
+  const char *src[14];
+#ifdef USE_SSL
+  char ssl_version[40];
+#endif
 #ifdef HAVE_LIBZ
-  len = msnprintf(ptr, left, " zlib/%s", zlibVersion());
-  left -= len;
-  ptr += len;
+  char z_version[40];
 #endif
 #ifdef HAVE_BROTLI
-  len = msnprintf(ptr, left, "%s", " brotli/");
-  left -= len;
-  ptr += len;
-  len = brotli_version(ptr, left);
-  left -= len;
-  ptr += len;
+  char br_version[40] = "brotli/";
 #endif
 #ifdef USE_ARES
-  /* this function is only present in c-ares, not in the original ares */
-  len = msnprintf(ptr, left, " c-ares/%s", ares_version(NULL));
-  left -= len;
-  ptr += len;
+  char cares_version[40];
+#endif
+#if defined(USE_LIBIDN2) || defined(USE_WIN32_IDN)
+  char idn_version[40];
+#endif
+#ifdef USE_LIBPSL
+  char psl_version[40];
+#endif
+#if defined(HAVE_ICONV) && defined(CURL_DOES_CONVERSIONS)
+  char iconv_version[40]="iconv";
+#endif
+#ifdef USE_SSH
+  char ssh_version[40];
+#endif
+#ifdef USE_NGHTTP2
+  char h2_version[40];
+#endif
+#ifdef ENABLE_QUIC
+  char h3_version[40];
+#endif
+#ifdef USE_LIBRTMP
+  char rtmp_version[40];
+#endif
+  int i = 0;
+  int j;
+
+  src[i++] = LIBCURL_NAME "/" LIBCURL_VERSION;
+#ifdef USE_SSL
+  Curl_ssl_version(ssl_version, sizeof(ssl_version));
+  src[i++] = ssl_version;
+#endif
+#ifdef HAVE_LIBZ
+  msnprintf(z_version, sizeof(z_version), "zlib/%s", zlibVersion());
+  src[i++] = z_version;
+#endif
+#ifdef HAVE_BROTLI
+  brotli_version(&br_version[7], sizeof(br_version) - 7);
+  src[i++] = br_version;
+#endif
+#ifdef USE_ARES
+  msnprintf(cares_version, sizeof(cares_version),
+            "c-ares/%s", ares_version(NULL));
+  src[i++] = cares_version;
 #endif
 #ifdef USE_LIBIDN2
   if(idn2_check_version(IDN2_VERSION)) {
-    len = msnprintf(ptr, left, " libidn2/%s", idn2_check_version(NULL));
-    left -= len;
-    ptr += len;
+    msnprintf(idn_version, sizeof(idn_version),
+              "libidn2/%s", idn2_check_version(NULL));
+    src[i++] = idn_version;
   }
+#elif defined(USE_WIN32_IDN)
+  msnprintf(idn_version, sizeof(idn_version), "WinIDN");
+  src[i++] = idn_version;
 #endif
+
 #ifdef USE_LIBPSL
-  len = msnprintf(ptr, left, " libpsl/%s", psl_get_version());
-  left -= len;
-  ptr += len;
-#endif
-#ifdef USE_WIN32_IDN
-  len = msnprintf(ptr, left, " WinIDN");
-  left -= len;
-  ptr += len;
+  msnprintf(psl_version, sizeof(psl_version), "libpsl/%s", psl_get_version());
+  src[i++] = psl_version;
 #endif
 #if defined(HAVE_ICONV) && defined(CURL_DOES_CONVERSIONS)
 #ifdef _LIBICONV_VERSION
-  len = msnprintf(ptr, left, " iconv/%d.%d",
-                  _LIBICONV_VERSION >> 8, _LIBICONV_VERSION & 255);
+  msnprintf(iconv_version, sizeof(iconv_version), "iconv/%d.%d",
+            _LIBICONV_VERSION >> 8, _LIBICONV_VERSION & 255);
 #else
-  /* version unknown */
-  len = msnprintf(ptr, left, " iconv");
+  /* version unknown, let the default stand */
 #endif /* _LIBICONV_VERSION */
-  left -= len;
-  ptr += len;
+  src[i++] = iconv_version;
 #endif
 #ifdef USE_SSH
-  if(left) {
-    *ptr++=' ';
-    left--;
-  }
-  len = Curl_ssh_version(ptr, left);
-  left -= len;
-  ptr += len;
+  Curl_ssh_version(ssh_version, sizeof(ssh_version));
+  src[i++] = ssh_version;
 #endif
 #ifdef USE_NGHTTP2
-  len = Curl_http2_ver(ptr, left);
-  left -= len;
-  ptr += len;
+  Curl_http2_ver(h2_version, sizeof(h2_version));
+  src[i++] = h2_version;
 #endif
 #ifdef ENABLE_QUIC
-  len = Curl_quic_ver(ptr, left);
-  left -= len;
-  ptr += len;
+  Curl_quic_ver(h3_version, sizeof(h3_version));
+  src[i++] = h3_version;
 #endif
 #ifdef USE_LIBRTMP
   {
@@ -188,27 +191,32 @@ char *curl_version(void)
     else
       suff[0] = '\0';
 
-    msnprintf(ptr, left, " librtmp/%d.%d%s",
+    msnprintf(rtmp_version, sizeof(rtmp_version), "librtmp/%d.%d%s",
               RTMP_LIB_VERSION >> 16, (RTMP_LIB_VERSION >> 8) & 0xff,
               suff);
-/*
-  If another lib version is added below this one, this code would
-  also have to do:
-
-    len = what msnprintf() returned
-
-    left -= len;
-    ptr += len;
-*/
+    src[i++] = rtmp_version;
   }
 #endif
 
-  /* Silent scan-build even if librtmp is not enabled. */
-  (void) left;
-  (void) ptr;
+  outp = &out[0];
+  outlen = sizeof(out);
+  for(j = 0; j < i; j++) {
+    size_t n = strlen(src[j]);
+    /* we need room for a space, the string and the final zero */
+    if(outlen <= (n + 2))
+      break;
+    if(j) {
+      /* prepend a space if not the first */
+      *outp++ = ' ';
+      outlen--;
+    }
+    memcpy(outp, src[j], n);
+    outp += n;
+    outlen -= n;
+  }
+  *outp = 0;
 
-  initialized = true;
-  return version;
+  return out;
 }
 
 /* data for curl_version_info
@@ -391,7 +399,6 @@ static curl_version_info_data version_info = {
 
 curl_version_info_data *curl_version_info(CURLversion stamp)
 {
-  static bool initialized;
 #if defined(USE_SSH)
   static char ssh_buffer[80];
 #endif
@@ -406,9 +413,6 @@ curl_version_info_data *curl_version_info(CURLversion stamp)
   static char brotli_buffer[80];
 #endif
 
-  if(initialized)
-    return &version_info;
-
 #ifdef USE_SSL
   Curl_ssl_version(ssl_buffer, sizeof(ssl_buffer));
   version_info.ssl_version = ssl_buffer;
@@ -476,7 +480,5 @@ curl_version_info_data *curl_version_info(CURLversion stamp)
 #endif
 
   (void)stamp; /* avoid compiler warnings, we don't use this */
-
-  initialized = true;
   return &version_info;
 }

lib/vquic/ngtcp2.c

@@ -641,7 +641,7 @@ int Curl_quic_ver(char *p, size_t len)
 {
   ngtcp2_info *ng2 = ngtcp2_version(0);
   nghttp3_info *ht3 = nghttp3_version(0);
-  return msnprintf(p, len, " ngtcp2/%s nghttp3/%s",
+  return msnprintf(p, len, "ngtcp2/%s nghttp3/%s",
                    ng2->version_str, ht3->version_str);
 }
 

lib/vquic/quiche.c

@@ -532,7 +532,7 @@ static ssize_t h3_stream_send(struct connectdata *conn,
  */
 int Curl_quic_ver(char *p, size_t len)
 {
-  return msnprintf(p, len, " quiche/%s", quiche_version());
+  return msnprintf(p, len, "quiche/%s", quiche_version());
 }
 
 /* Index where :authority header field will appear in request header

lib/vtls/vtls.h

@@ -262,7 +262,6 @@ bool Curl_ssl_false_start(void);
 #define Curl_ssl_send(a,b,c,d,e) -1
 #define Curl_ssl_recv(a,b,c,d,e) -1
 #define Curl_ssl_initsessions(x,y) CURLE_OK
-#define Curl_ssl_version(x,y) 0
 #define Curl_ssl_data_pending(x,y) 0
 #define Curl_ssl_check_cxn(x) 0
 #define Curl_ssl_free_certinfo(x) Curl_nop_stmt