Merge pull request #188 from ctiller/bprintf

Remove more complicated sprintf usage from the libraries

src/core/channel/call_op_string.c

@@ -41,110 +41,86 @@
 #include <grpc/support/alloc.h>
 #include <grpc/support/useful.h>
 
-#define MAX_APPEND 1024
+static void put_metadata(gpr_strvec *b, grpc_mdelem *md) {
+  gpr_strvec_add(b, gpr_strdup(" key="));
+  gpr_strvec_add(b, gpr_hexdump((char *)GPR_SLICE_START_PTR(md->key->slice),
+                    GPR_SLICE_LENGTH(md->key->slice), GPR_HEXDUMP_PLAINTEXT));
 
-typedef struct {
-  size_t cap;
-  size_t len;
-  char *buffer;
-} buf;
-
-static void bprintf(buf *b, const char *fmt, ...) {
-  va_list arg;
-  if (b->len + MAX_APPEND > b->cap) {
-    b->cap = GPR_MAX(b->len + MAX_APPEND, b->cap * 3 / 2);
-    b->buffer = gpr_realloc(b->buffer, b->cap);
-  }
-  va_start(arg, fmt);
-  b->len += vsprintf(b->buffer + b->len, fmt, arg);
-  va_end(arg);
-}
-
-static void bputs(buf *b, const char *s) {
-  size_t slen = strlen(s);
-  if (b->len + slen + 1 > b->cap) {
-    b->cap = GPR_MAX(b->len + slen + 1, b->cap * 3 / 2);
-    b->buffer = gpr_realloc(b->buffer, b->cap);
-  }
-  strcat(b->buffer, s);
-  b->len += slen;
-}
-
-static void put_metadata(buf *b, grpc_mdelem *md) {
-  char *txt;
-
-  txt = gpr_hexdump((char *)GPR_SLICE_START_PTR(md->key->slice),
-                    GPR_SLICE_LENGTH(md->key->slice), GPR_HEXDUMP_PLAINTEXT);
-  bputs(b, " key=");
-  bputs(b, txt);
-  gpr_free(txt);
-
-  txt = gpr_hexdump((char *)GPR_SLICE_START_PTR(md->value->slice),
-                    GPR_SLICE_LENGTH(md->value->slice), GPR_HEXDUMP_PLAINTEXT);
-  bputs(b, " value=");
-  bputs(b, txt);
-  gpr_free(txt);
+  gpr_strvec_add(b, gpr_strdup(" value="));
+  gpr_strvec_add(b, gpr_hexdump((char *)GPR_SLICE_START_PTR(md->value->slice),
+                    GPR_SLICE_LENGTH(md->value->slice), GPR_HEXDUMP_PLAINTEXT));
 }
 
 char *grpc_call_op_string(grpc_call_op *op) {
-  buf b = {0, 0, 0};
+  char *tmp;
+  char *out;
+
+  gpr_strvec b;
+  gpr_strvec_init(&b);
 
   switch (op->dir) {
     case GRPC_CALL_DOWN:
-      bprintf(&b, ">");
+      gpr_strvec_add(&b, gpr_strdup(">"));
       break;
     case GRPC_CALL_UP:
-      bprintf(&b, "<");
+      gpr_strvec_add(&b, gpr_strdup("<"));
       break;
   }
   switch (op->type) {
     case GRPC_SEND_METADATA:
-      bprintf(&b, "SEND_METADATA");
+      gpr_strvec_add(&b, gpr_strdup("SEND_METADATA"));
       put_metadata(&b, op->data.metadata);
       break;
     case GRPC_SEND_DEADLINE:
-      bprintf(&b, "SEND_DEADLINE %d.%09d", op->data.deadline.tv_sec,
+      gpr_asprintf(&tmp, "SEND_DEADLINE %d.%09d", op->data.deadline.tv_sec,
               op->data.deadline.tv_nsec);
+      gpr_strvec_add(&b, tmp);
       break;
     case GRPC_SEND_START:
-      bprintf(&b, "SEND_START pollset=%p", op->data.start.pollset);
+      gpr_asprintf(&tmp, "SEND_START pollset=%p", op->data.start.pollset);
+      gpr_strvec_add(&b, tmp);
       break;
     case GRPC_SEND_MESSAGE:
-      bprintf(&b, "SEND_MESSAGE");
+      gpr_strvec_add(&b, gpr_strdup("SEND_MESSAGE"));
       break;
     case GRPC_SEND_FINISH:
-      bprintf(&b, "SEND_FINISH");
+      gpr_strvec_add(&b, gpr_strdup("SEND_FINISH"));
       break;
     case GRPC_REQUEST_DATA:
-      bprintf(&b, "REQUEST_DATA");
+      gpr_strvec_add(&b, gpr_strdup("REQUEST_DATA"));
       break;
     case GRPC_RECV_METADATA:
-      bprintf(&b, "RECV_METADATA");
+      gpr_strvec_add(&b, gpr_strdup("RECV_METADATA"));
       put_metadata(&b, op->data.metadata);
       break;
     case GRPC_RECV_DEADLINE:
-      bprintf(&b, "RECV_DEADLINE %d.%09d", op->data.deadline.tv_sec,
+      gpr_asprintf(&tmp, "RECV_DEADLINE %d.%09d", op->data.deadline.tv_sec,
               op->data.deadline.tv_nsec);
+      gpr_strvec_add(&b, tmp);
       break;
     case GRPC_RECV_END_OF_INITIAL_METADATA:
-      bprintf(&b, "RECV_END_OF_INITIAL_METADATA");
+      gpr_strvec_add(&b, gpr_strdup("RECV_END_OF_INITIAL_METADATA"));
       break;
     case GRPC_RECV_MESSAGE:
-      bprintf(&b, "RECV_MESSAGE");
+      gpr_strvec_add(&b, gpr_strdup("RECV_MESSAGE"));
       break;
     case GRPC_RECV_HALF_CLOSE:
-      bprintf(&b, "RECV_HALF_CLOSE");
+      gpr_strvec_add(&b, gpr_strdup("RECV_HALF_CLOSE"));
       break;
     case GRPC_RECV_FINISH:
-      bprintf(&b, "RECV_FINISH");
+      gpr_strvec_add(&b, gpr_strdup("RECV_FINISH"));
       break;
     case GRPC_CANCEL_OP:
-      bprintf(&b, "CANCEL_OP");
+      gpr_strvec_add(&b, gpr_strdup("CANCEL_OP"));
       break;
   }
-  bprintf(&b, " flags=0x%08x", op->flags);
+  gpr_asprintf(&tmp, " flags=0x%08x", op->flags);
+  gpr_strvec_add(&b, tmp);
+
+  out = gpr_strvec_flatten(&b, NULL);
+  gpr_strvec_destroy(&b);
 
-  return b.buffer;
+  return out;
 }
 
 void grpc_call_log_op(char *file, int line, gpr_log_severity severity,

src/core/channel/connected_channel.c

@@ -450,6 +450,7 @@ static void recv_batch(void *user_data, grpc_transport *transport,
                    (int)calld->incoming_message.length,
                    (int)calld->incoming_message_length);
       recv_error(chand, calld, __LINE__, message);
+      gpr_free(message);
     }
     call_op.type = GRPC_RECV_HALF_CLOSE;
     call_op.dir = GRPC_CALL_UP;

src/core/httpcli/format_request.c

@@ -37,67 +37,57 @@
 #include <stdio.h>
 #include <string.h>
 
+#include "src/core/support/string.h"
 #include <grpc/support/alloc.h>
 #include <grpc/support/slice.h>
 #include <grpc/support/useful.h>
 
-typedef struct {
-  size_t length;
-  size_t capacity;
-  char *data;
-} sbuf;
-
-static void sbuf_append(sbuf *buf, const char *bytes, size_t len) {
-  if (buf->length + len > buf->capacity) {
-    buf->capacity = GPR_MAX(buf->length + len, buf->capacity * 3 / 2);
-    buf->data = gpr_realloc(buf->data, buf->capacity);
-  }
-  memcpy(buf->data + buf->length, bytes, len);
-  buf->length += len;
-}
-
-static void sbprintf(sbuf *buf, const char *fmt, ...) {
-  char temp[GRPC_HTTPCLI_MAX_HEADER_LENGTH];
-  size_t len;
-  va_list args;
-
-  va_start(args, fmt);
-  len = vsprintf(temp, fmt, args);
-  va_end(args);
-
-  sbuf_append(buf, temp, len);
-}
-
-static void fill_common_header(const grpc_httpcli_request *request, sbuf *buf) {
+static void fill_common_header(const grpc_httpcli_request *request, gpr_strvec *buf) {
   size_t i;
-  sbprintf(buf, "%s HTTP/1.0\r\n", request->path);
+  gpr_strvec_add(buf, gpr_strdup(request->path));
+  gpr_strvec_add(buf, gpr_strdup(" HTTP/1.0\r\n"));
   /* just in case some crazy server really expects HTTP/1.1 */
-  sbprintf(buf, "Host: %s\r\n", request->host);
-  sbprintf(buf, "Connection: close\r\n");
-  sbprintf(buf, "User-Agent: %s\r\n", GRPC_HTTPCLI_USER_AGENT);
+  gpr_strvec_add(buf, gpr_strdup("Host: "));
+  gpr_strvec_add(buf, gpr_strdup(request->host));
+  gpr_strvec_add(buf, gpr_strdup("\r\n"));
+  gpr_strvec_add(buf, gpr_strdup("Connection: close\r\n"));
+  gpr_strvec_add(buf, gpr_strdup("User-Agent: "GRPC_HTTPCLI_USER_AGENT"\r\n"));
   /* user supplied headers */
   for (i = 0; i < request->hdr_count; i++) {
-    sbprintf(buf, "%s: %s\r\n", request->hdrs[i].key, request->hdrs[i].value);
+    gpr_strvec_add(buf, gpr_strdup(request->hdrs[i].key));
+    gpr_strvec_add(buf, gpr_strdup(": "));
+    gpr_strvec_add(buf, gpr_strdup(request->hdrs[i].value));
+    gpr_strvec_add(buf, gpr_strdup("\r\n"));
   }
 }
 
 gpr_slice grpc_httpcli_format_get_request(const grpc_httpcli_request *request) {
-  sbuf out = {0, 0, NULL};
+  gpr_strvec out;
+  char *flat;
+  size_t flat_len;
 
-  sbprintf(&out, "GET ");
+  gpr_strvec_init(&out);
+  gpr_strvec_add(&out, gpr_strdup("GET "));
   fill_common_header(request, &out);
-  sbprintf(&out, "\r\n");
+  gpr_strvec_add(&out, gpr_strdup("\r\n"));
 
-  return gpr_slice_new(out.data, out.length, gpr_free);
+  flat = gpr_strvec_flatten(&out, &flat_len);
+  gpr_strvec_destroy(&out);
+
+  return gpr_slice_new(flat, flat_len, gpr_free);
 }
 
 gpr_slice grpc_httpcli_format_post_request(const grpc_httpcli_request *request,
                                            const char *body_bytes,
                                            size_t body_size) {
-  sbuf out = {0, 0, NULL};
+  gpr_strvec out;
+  char *tmp;
+  size_t out_len;
   size_t i;
 
-  sbprintf(&out, "POST ");
+  gpr_strvec_init(&out);
+
+  gpr_strvec_add(&out, gpr_strdup("POST "));
   fill_common_header(request, &out);
   if (body_bytes) {
     gpr_uint8 has_content_type = 0;
@@ -108,14 +98,18 @@ gpr_slice grpc_httpcli_format_post_request(const grpc_httpcli_request *request,
       }
     }
     if (!has_content_type) {
-      sbprintf(&out, "Content-Type: text/plain\r\n");
+      gpr_strvec_add(&out, gpr_strdup("Content-Type: text/plain\r\n"));
     }
-    sbprintf(&out, "Content-Length: %lu\r\n", (unsigned long)body_size);
+    gpr_asprintf(&tmp, "Content-Length: %lu\r\n", (unsigned long)body_size);
+    gpr_strvec_add(&out, tmp);
   }
-  sbprintf(&out, "\r\n");
+  gpr_strvec_add(&out, gpr_strdup("\r\n"));
+  tmp = gpr_strvec_flatten(&out, &out_len);
   if (body_bytes) {
-    sbuf_append(&out, body_bytes, body_size);
+    tmp = gpr_realloc(tmp, out_len + body_size);
+    memcpy(tmp + out_len, body_bytes, body_size);
+    out_len += body_size;
   }
 
-  return gpr_slice_new(out.data, out.length, gpr_free);
+  return gpr_slice_new(tmp, out_len, gpr_free);
 }

src/core/support/string.c

@@ -152,3 +152,49 @@ int gpr_ltoa(long value, char *string) {
   string[i] = 0;
   return i;
 }
+
+char *gpr_strjoin(const char **strs, size_t nstrs, size_t *final_length) {
+  size_t out_length = 0;
+  size_t i;
+  char *out;
+  for (i = 0; i < nstrs; i++) {
+    out_length += strlen(strs[i]);
+  }
+  out_length += 1;  /* null terminator */
+  out = gpr_malloc(out_length);
+  out_length = 0;
+  for (i = 0; i < nstrs; i++) {
+    size_t slen = strlen(strs[i]);
+    memcpy(out + out_length, strs[i], slen);
+    out_length += slen;
+  }
+  out[out_length] = 0;
+  if (final_length != NULL) {
+    *final_length = out_length;
+  }
+  return out;
+}
+
+void gpr_strvec_init(gpr_strvec *sv) {
+  memset(sv, 0, sizeof(*sv));
+}
+
+void gpr_strvec_destroy(gpr_strvec *sv) {
+  size_t i;
+  for (i = 0; i < sv->count; i++) {
+    gpr_free(sv->strs[i]);
+  }
+  gpr_free(sv->strs);
+}
+
+void gpr_strvec_add(gpr_strvec *sv, char *str) {
+  if (sv->count == sv->capacity) {
+    sv->capacity = GPR_MAX(sv->capacity + 8, sv->capacity * 2);
+    sv->strs = gpr_realloc(sv->strs, sizeof(char*) * sv->capacity);
+  }
+  sv->strs[sv->count++] = str;
+}
+
+char *gpr_strvec_flatten(gpr_strvec *sv, size_t *final_length) {
+  return gpr_strjoin((const char**)sv->strs, sv->count, final_length);
+}

src/core/support/string.h

@@ -81,6 +81,27 @@ void gpr_reverse_bytes(char *str, int len);
    the result is undefined. */
 int gpr_asprintf(char **strp, const char *format, ...);
 
+/* Join a set of strings, returning the resulting string.
+   Total combined length (excluding null terminator) is returned in total_length
+   if it is non-null. */
+char *gpr_strjoin(const char **strs, size_t nstrs, size_t *total_length);
+
+/* A vector of strings... for building up a final string one piece at a time */
+typedef struct {
+  char **strs;
+  size_t count;
+  size_t capacity;
+} gpr_strvec;
+
+/* Initialize/destroy */
+void gpr_strvec_init(gpr_strvec *strs);
+void gpr_strvec_destroy(gpr_strvec *strs);
+/* Add a string to a strvec, takes ownership of the string */
+void gpr_strvec_add(gpr_strvec *strs, char *add);
+/* Return a joined string with all added substrings, optionally setting
+   total_length as per gpr_strjoin */
+char *gpr_strvec_flatten(gpr_strvec *strs, size_t *total_length);
+
 #ifdef __cplusplus
 }
 #endif

src/core/surface/event_string.c

@@ -38,8 +38,10 @@
 #include "src/core/support/string.h"
 #include <grpc/byte_buffer.h>
 
-static size_t addhdr(char *p, grpc_event *ev) {
-  return sprintf(p, "tag:%p call:%p", ev->tag, (void *)ev->call);
+static void addhdr(gpr_strvec *buf, grpc_event *ev) {
+  char *tmp;
+  gpr_asprintf(&tmp, "tag:%p call:%p", ev->tag, (void *)ev->call);
+  gpr_strvec_add(buf, tmp);
 }
 
 static const char *errstr(grpc_op_error err) {
@@ -52,72 +54,84 @@ static const char *errstr(grpc_op_error err) {
   return "UNKNOWN_UNKNOWN";
 }
 
-static size_t adderr(char *p, grpc_op_error err) {
-  return sprintf(p, " err=%s", errstr(err));
+static void adderr(gpr_strvec *buf, grpc_op_error err) {
+  char *tmp;
+  gpr_asprintf(&tmp, " err=%s", errstr(err));
+  gpr_strvec_add(buf, tmp);
 }
 
 char *grpc_event_string(grpc_event *ev) {
-  char buffer[1024];
-  char *p = buffer;
+  char *out;
+  char *tmp;
+  gpr_strvec buf;
 
   if (ev == NULL) return gpr_strdup("null");
 
+  gpr_strvec_init(&buf);
+
   switch (ev->type) {
     case GRPC_SERVER_SHUTDOWN:
-      p += sprintf(p, "SERVER_SHUTDOWN");
+      gpr_strvec_add(&buf, gpr_strdup("SERVER_SHUTDOWN"));
       break;
     case GRPC_QUEUE_SHUTDOWN:
-      p += sprintf(p, "QUEUE_SHUTDOWN");
+      gpr_strvec_add(&buf, gpr_strdup("QUEUE_SHUTDOWN"));
       break;
     case GRPC_READ:
-      p += sprintf(p, "READ: ");
-      p += addhdr(p, ev);
+      gpr_strvec_add(&buf, gpr_strdup("READ: "));
+      addhdr(&buf, ev);
       if (ev->data.read) {
-        p += sprintf(p, " %d bytes",
+        gpr_asprintf(&tmp, " %d bytes",
                      (int)grpc_byte_buffer_length(ev->data.read));
+        gpr_strvec_add(&buf, tmp);
       } else {
-        p += sprintf(p, " end-of-stream");
+        gpr_strvec_add(&buf, gpr_strdup(" end-of-stream"));
       }
       break;
     case GRPC_INVOKE_ACCEPTED:
-      p += sprintf(p, "INVOKE_ACCEPTED: ");
-      p += addhdr(p, ev);
-      p += adderr(p, ev->data.invoke_accepted);
+      gpr_strvec_add(&buf, gpr_strdup("INVOKE_ACCEPTED: "));
+      addhdr(&buf, ev);
+      adderr(&buf, ev->data.invoke_accepted);
       break;
     case GRPC_WRITE_ACCEPTED:
-      p += sprintf(p, "WRITE_ACCEPTED: ");
-      p += addhdr(p, ev);
-      p += adderr(p, ev->data.write_accepted);
+      gpr_strvec_add(&buf, gpr_strdup("WRITE_ACCEPTED: "));
+      addhdr(&buf, ev);
+      adderr(&buf, ev->data.write_accepted);
       break;
     case GRPC_FINISH_ACCEPTED:
-      p += sprintf(p, "FINISH_ACCEPTED: ");
-      p += addhdr(p, ev);
-      p += adderr(p, ev->data.write_accepted);
+      gpr_strvec_add(&buf, gpr_strdup("FINISH_ACCEPTED: "));
+      addhdr(&buf, ev);
+      adderr(&buf, ev->data.write_accepted);
       break;
     case GRPC_CLIENT_METADATA_READ:
-      p += sprintf(p, "CLIENT_METADATA_READ: ");
-      p += addhdr(p, ev);
-      p += sprintf(p, " %d elements", (int)ev->data.client_metadata_read.count);
+      gpr_strvec_add(&buf, gpr_strdup("CLIENT_METADATA_READ: "));
+      addhdr(&buf, ev);
+      gpr_asprintf(&tmp, " %d elements",
+                   (int)ev->data.client_metadata_read.count);
+      gpr_strvec_add(&buf, tmp);
       break;
     case GRPC_FINISHED:
-      p += sprintf(p, "FINISHED: ");
-      p += addhdr(p, ev);
-      p += sprintf(p, " status=%d details='%s' %d metadata elements",
+      gpr_strvec_add(&buf, gpr_strdup("FINISHED: "));
+      addhdr(&buf, ev);
+      gpr_asprintf(&tmp, " status=%d details='%s' %d metadata elements",
                    ev->data.finished.status, ev->data.finished.details,
                    (int)ev->data.finished.metadata_count);
+      gpr_strvec_add(&buf, tmp);
       break;
     case GRPC_SERVER_RPC_NEW:
-      p += sprintf(p, "SERVER_RPC_NEW: ");
-      p += addhdr(p, ev);
-      p += sprintf(p, " method='%s' host='%s' %d metadata elements",
+      gpr_strvec_add(&buf, gpr_strdup("SERVER_RPC_NEW: "));
+      addhdr(&buf, ev);
+      gpr_asprintf(&tmp, " method='%s' host='%s' %d metadata elements",
                    ev->data.server_rpc_new.method, ev->data.server_rpc_new.host,
                    (int)ev->data.server_rpc_new.metadata_count);
+      gpr_strvec_add(&buf, tmp);
       break;
     case GRPC_COMPLETION_DO_NOT_USE:
-      p += sprintf(p, "DO_NOT_USE (this is a bug)");
-      p += addhdr(p, ev);
+      gpr_strvec_add(&buf, gpr_strdup("DO_NOT_USE (this is a bug)"));
+      addhdr(&buf, ev);
       break;
   }
 
-  return gpr_strdup(buffer);
+  out = gpr_strvec_flatten(&buf, NULL);
+  gpr_strvec_destroy(&buf);
+  return out;
 }

test/core/channel/metadata_buffer_test.c

@@ -32,6 +32,7 @@
  */
 
 #include "src/core/channel/metadata_buffer.h"
+#include "src/core/support/string.h"
 #include <grpc/support/alloc.h>
 #include <grpc/support/log.h>
 #include "test/core/util/test_config.h"
@@ -42,12 +43,12 @@
 /* construct a buffer with some prefix followed by an integer converted to
    a string */
 static gpr_slice construct_buffer(size_t prefix_length, size_t index) {
-  gpr_slice buffer = gpr_slice_malloc(prefix_length + 32);
+  gpr_slice buffer = gpr_slice_malloc(prefix_length + GPR_LTOA_MIN_BUFSIZE);
   memset(GPR_SLICE_START_PTR(buffer), 'a', prefix_length);
   GPR_SLICE_SET_LENGTH(
-      buffer, prefix_length +
-                  sprintf((char *)GPR_SLICE_START_PTR(buffer) + prefix_length,
-                          "%d", (int)index));
+      buffer,
+      prefix_length +
+          gpr_ltoa(index, (char *)GPR_SLICE_START_PTR(buffer) + prefix_length));
   return buffer;
 }
 

test/core/end2end/cq_verifier.c

@@ -231,100 +231,91 @@ static void verify_matches(expectation *e, grpc_event *ev) {
   }
 }
 
-static char *metadata_expectation_string(metadata *md) {
-  size_t len;
+static void metadata_expectation(gpr_strvec *buf, metadata *md) {
   size_t i;
-  char *out;
-  char *p;
+  char *tmp;
 
-  if (!md) return gpr_strdup("nil");
-
-  for (len = 0, i = 0; i < md->count; i++) {
-    len += strlen(md->keys[i]);
-    len += strlen(md->values[i]);
-  }
-  len += 3 + md->count;
-
-  p = out = gpr_malloc(len);
-  *p++ = '{';
+  if (!md) {
+    gpr_strvec_add(buf, gpr_strdup("nil"));
+  } else {
     for (i = 0; i < md->count; i++) {
-    if (i) *p++ = ',';
-    p += sprintf(p, "%s:%s", md->keys[i], md->values[i]);
+      gpr_asprintf(&tmp, "%c%s:%s", i ? ',' : '{', md->keys[i], md->values[i]);
+      gpr_strvec_add(buf, tmp);
+    }
+    gpr_strvec_add(buf, gpr_strdup("}"));
   }
-  *p++ = '}';
-  *p++ = 0;
-  return out;
 }
 
-static size_t expectation_to_string(char *out, expectation *e) {
+static void expectation_to_strvec(gpr_strvec *buf, expectation *e) {
   gpr_timespec timeout;
-  char *str = NULL;
-  size_t len;
+  char *tmp;
 
   switch (e->type) {
     case GRPC_FINISH_ACCEPTED:
-      return sprintf(out, "GRPC_FINISH_ACCEPTED result=%d",
+      gpr_asprintf(&tmp, "GRPC_FINISH_ACCEPTED result=%d",
                      e->data.finish_accepted);
+      gpr_strvec_add(buf, tmp);
+      break;
     case GRPC_WRITE_ACCEPTED:
-      return sprintf(out, "GRPC_WRITE_ACCEPTED result=%d",
+      gpr_asprintf(&tmp, "GRPC_WRITE_ACCEPTED result=%d",
                      e->data.write_accepted);
+      gpr_strvec_add(buf, tmp);
+      break;
     case GRPC_INVOKE_ACCEPTED:
-      return sprintf(out, "GRPC_INVOKE_ACCEPTED");
+      gpr_strvec_add(buf, gpr_strdup("GRPC_INVOKE_ACCEPTED"));
+      break;
     case GRPC_SERVER_RPC_NEW:
       timeout = gpr_time_sub(e->data.server_rpc_new.deadline, gpr_now());
-      return sprintf(out, "GRPC_SERVER_RPC_NEW method=%s host=%s timeout=%fsec",
+      gpr_asprintf(&tmp, "GRPC_SERVER_RPC_NEW method=%s host=%s timeout=%fsec",
                      e->data.server_rpc_new.method, e->data.server_rpc_new.host,
                      timeout.tv_sec + 1e-9 * timeout.tv_nsec);
+      gpr_strvec_add(buf, tmp);
+      break;
     case GRPC_CLIENT_METADATA_READ:
-      str = metadata_expectation_string(e->data.client_metadata_read);
-      len = sprintf(out, "GRPC_CLIENT_METADATA_READ %s", str);
-      gpr_free(str);
-      return len;
+      gpr_strvec_add(buf, gpr_strdup("GRPC_CLIENT_METADATA_READ "));
+      metadata_expectation(buf, e->data.client_metadata_read);
+      break;
     case GRPC_FINISHED:
-      str = metadata_expectation_string(e->data.finished.metadata);
-      len = sprintf(out, "GRPC_FINISHED status=%d details=%s %s",
-                    e->data.finished.status, e->data.finished.details, str);
-      gpr_free(str);
-      return len;
+      gpr_asprintf(&tmp, "GRPC_FINISHED status=%d details=%s ",
+                    e->data.finished.status, e->data.finished.details);
+      gpr_strvec_add(buf, tmp);
+      metadata_expectation(buf, e->data.finished.metadata);
+      break;
     case GRPC_READ:
-      if (e->data.read) {
-        str =
-            gpr_hexdump((char *)GPR_SLICE_START_PTR(*e->data.read),
-                        GPR_SLICE_LENGTH(*e->data.read), GPR_HEXDUMP_PLAINTEXT);
-      }
-      len = sprintf(out, "GRPC_READ data=%s", str);
-      gpr_free(str);
-      return len;
+      gpr_strvec_add(buf, gpr_strdup("GRPC_READ data="));
+      gpr_strvec_add(buf, gpr_hexdump((char *)GPR_SLICE_START_PTR(*e->data.read),
+                        GPR_SLICE_LENGTH(*e->data.read), GPR_HEXDUMP_PLAINTEXT));
+      break;
     case GRPC_SERVER_SHUTDOWN:
-      return sprintf(out, "GRPC_SERVER_SHUTDOWN");
+      gpr_strvec_add(buf, gpr_strdup("GRPC_SERVER_SHUTDOWN"));
+      break;
     case GRPC_COMPLETION_DO_NOT_USE:
     case GRPC_QUEUE_SHUTDOWN:
       gpr_log(GPR_ERROR, "not implemented");
       abort();
       break;
   }
-  return 0;
 }
 
-static char *expectations_to_string(cq_verifier *v) {
-  /* allocate a large buffer: we're about to crash anyway */
-  char *buffer = gpr_malloc(32 * 1024 * 1024);
-  char *p = buffer;
+static void expectations_to_strvec(gpr_strvec *buf, cq_verifier *v) {
   expectation *e;
 
   for (e = v->expect.next; e != &v->expect; e = e->next) {
-    p += expectation_to_string(p, e);
-    *p++ = '\n';
+    expectation_to_strvec(buf, e);
+    gpr_strvec_add(buf, gpr_strdup("\n"));
   }
-
-  *p = 0;
-  return buffer;
 }
 
 static void fail_no_event_received(cq_verifier *v) {
-  char *expectations = expectations_to_string(v);
-  gpr_log(GPR_ERROR, "no event received, but expected:\n%s", expectations);
-  gpr_free(expectations);
+  gpr_strvec buf;
+  char *msg;
+  gpr_strvec_init(&buf);
+  gpr_strvec_add(&buf, gpr_strdup("no event received, but expected:\n"));
+  expectations_to_strvec(&buf, v);
+  msg = gpr_strvec_flatten(&buf, NULL);
+  gpr_log(GPR_ERROR, "%s", msg);
+  gpr_strvec_destroy(&buf);
+  gpr_free(msg);
   abort();
 }
 
@@ -333,9 +324,10 @@ void cq_verify(cq_verifier *v) {
       gpr_time_add(gpr_now(), gpr_time_from_micros(10 * GPR_US_PER_SEC));
   grpc_event *ev;
   expectation *e;
+  char *s;
+  gpr_strvec have_tags;
 
-  char have_tags[512] = {0};
-  char *phave = have_tags;
+  gpr_strvec_init(&have_tags);
 
   while (v->expect.next != &v->expect) {
     ev = grpc_completion_queue_next(v->cq, deadline);
@@ -344,7 +336,8 @@ void cq_verify(cq_verifier *v) {
     }
 
     for (e = v->expect.next; e != &v->expect; e = e->next) {
-      phave += sprintf(phave, " %p", e->tag);
+      gpr_asprintf(&s, " %p", e->tag);
+      gpr_strvec_add(&have_tags, s);
       if (e->tag == ev->tag) {
         verify_matches(e, ev);
         e->next->prev = e->prev;
@@ -354,15 +347,20 @@ void cq_verify(cq_verifier *v) {
       }
     }
     if (e == &v->expect) {
-      char *s = grpc_event_string(ev);
+      s = grpc_event_string(ev);
       gpr_log(GPR_ERROR, "event not found: %s", s);
-      gpr_log(GPR_ERROR, "have tags:%s", have_tags);
       gpr_free(s);
+      s = gpr_strvec_flatten(&have_tags, NULL);
+      gpr_log(GPR_ERROR, "have tags:%s", s);
+      gpr_free(s);
+      gpr_strvec_destroy(&have_tags);
       abort();
     }
 
     grpc_event_finish(ev);
   }
+
+  gpr_strvec_destroy(&have_tags);
 }
 
 void cq_verify_empty(cq_verifier *v) {

test/core/end2end/tests/census_simple_request.c

@@ -37,6 +37,7 @@
 #include <string.h>
 #include <unistd.h>
 
+#include "src/core/support/string.h"
 #include <grpc/byte_buffer.h>
 #include <grpc/support/alloc.h>
 #include <grpc/support/log.h>
@@ -145,7 +146,7 @@ static void test_body(grpc_end2end_test_fixture f) {
 static void test_invoke_request_with_census(
     grpc_end2end_test_config config, const char *name,
     void (*body)(grpc_end2end_test_fixture f)) {
-  char fullname[64];
+  char *fullname;
   grpc_end2end_test_fixture f;
   grpc_arg client_arg, server_arg;
   grpc_channel_args client_args, server_args;
@@ -163,11 +164,12 @@ static void test_invoke_request_with_census(
   server_args.num_args = 1;
   server_args.args = &server_arg;
 
-  sprintf(fullname, "%s/%s", __FUNCTION__, name);
+  gpr_asprintf(&fullname, "%s/%s", __FUNCTION__, name);
   f = begin_test(config, fullname, &client_args, &server_args);
   body(f);
   end_test(&f);
   config.tear_down_data(&f);
+  gpr_free(fullname);
 }
 
 void grpc_end2end_tests(grpc_end2end_test_config config) {

test/core/end2end/tests/simple_request.c

@@ -37,6 +37,7 @@
 #include <string.h>
 #include <unistd.h>
 
+#include "src/core/support/string.h"
 #include <grpc/byte_buffer.h>
 #include <grpc/support/alloc.h>
 #include <grpc/support/log.h>
@@ -198,15 +199,16 @@ static void simple_request_body2(grpc_end2end_test_fixture f) {
 static void test_invoke_simple_request(
     grpc_end2end_test_config config, const char *name,
     void (*body)(grpc_end2end_test_fixture f)) {
-  char fullname[64];
+  char *fullname;
   grpc_end2end_test_fixture f;
 
-  sprintf(fullname, "%s/%s", __FUNCTION__, name);
+  gpr_asprintf(&fullname, "%s/%s", __FUNCTION__, name);
 
   f = begin_test(config, fullname, NULL, NULL);
   body(f);
   end_test(&f);
   config.tear_down_data(&f);
+  gpr_free(fullname);
 }
 
 static void test_invoke_10_simple_requests(grpc_end2end_test_config config) {

test/core/security/credentials_test.c

@@ -498,10 +498,8 @@ static void validate_service_account_http_request(
   char *expected_body = NULL;
   GPR_ASSERT(body != NULL);
   GPR_ASSERT(body_size != 0);
-  expected_body = gpr_malloc(strlen(expected_service_account_http_body_prefix) +
-                             strlen(test_signed_jwt) + 1);
-  sprintf(expected_body, "%s%s", expected_service_account_http_body_prefix,
-          test_signed_jwt);
+  gpr_asprintf(&expected_body, "%s%s",
+               expected_service_account_http_body_prefix, test_signed_jwt);
   GPR_ASSERT(strlen(expected_body) == body_size);
   GPR_ASSERT(!memcmp(expected_body, body, body_size));
   gpr_free(expected_body);

test/core/statistics/hash_table_test.c

@@ -38,6 +38,7 @@
 #include "src/core/statistics/hash_table.h"
 
 #include "src/core/support/murmur_hash.h"
+#include "src/core/support/string.h"
 #include <grpc/support/alloc.h>
 #include <grpc/support/log.h>
 #include <grpc/support/time.h>
@@ -187,15 +188,15 @@ static void test_insertion_and_deletion_with_high_collision_rate(void) {
   census_ht_option opt = {CENSUS_HT_POINTER, 13,   &force_collision,
                           &cmp_str_keys,     NULL, NULL};
   census_ht* ht = census_ht_create(&opt);
-  char key_str[1000][10];
+  char key_str[1000][GPR_LTOA_MIN_BUFSIZE];
   gpr_uint64 val = 0;
   int i = 0;
   for (i = 0; i < 1000; i++) {
     census_ht_key key;
     key.ptr = key_str[i];
-    sprintf(key_str[i], "%d", i);
+    gpr_ltoa(i, key_str[i]);
     census_ht_insert(ht, key, (void*)(&val));
-    printf("%d\n", i);
+    gpr_log(GPR_INFO, "%d\n", i);
     GPR_ASSERT(census_ht_get_size(ht) == (i + 1));
   }
   for (i = 0; i < 1000; i++) {

test/core/transport/chttp2/hpack_table_test.c

@@ -36,6 +36,7 @@
 #include <string.h>
 #include <stdio.h>
 
+#include "src/core/support/string.h"
 #include <grpc/support/alloc.h>
 #include <grpc/support/log.h>
 #include "test/core/util/test_config.h"
@@ -131,8 +132,8 @@ static void test_static_lookup(void) {
 static void test_many_additions(void) {
   grpc_chttp2_hptbl tbl;
   int i;
-  char key[32];
-  char value[32];
+  char *key;
+  char *value;
   grpc_mdctx *mdctx;
 
   LOG_TEST();
@@ -141,14 +142,18 @@ static void test_many_additions(void) {
   grpc_chttp2_hptbl_init(&tbl, mdctx);
 
   for (i = 0; i < 1000000; i++) {
-    sprintf(key, "K:%d", i);
-    sprintf(value, "VALUE:%d", i);
+    gpr_asprintf(&key, "K:%d", i);
+    gpr_asprintf(&value, "VALUE:%d", i);
     grpc_chttp2_hptbl_add(&tbl, grpc_mdelem_from_strings(mdctx, key, value));
     assert_index(&tbl, 1 + GRPC_CHTTP2_LAST_STATIC_ENTRY, key, value);
+    gpr_free(key);
+    gpr_free(value);
     if (i) {
-      sprintf(key, "K:%d", i - 1);
-      sprintf(value, "VALUE:%d", i - 1);
+      gpr_asprintf(&key, "K:%d", i - 1);
+      gpr_asprintf(&value, "VALUE:%d", i - 1);
       assert_index(&tbl, 2 + GRPC_CHTTP2_LAST_STATIC_ENTRY, key, value);
+      gpr_free(key);
+      gpr_free(value);
     }
   }
 
@@ -226,7 +231,7 @@ static void test_find(void) {
 
   /* overflow the string buffer, check find still works */
   for (i = 0; i < 10000; i++) {
-    sprintf(buffer, "%d", i);
+    gpr_ltoa(i, buffer);
     grpc_chttp2_hptbl_add(&tbl,
                           grpc_mdelem_from_strings(mdctx, "test", buffer));
   }
@@ -245,7 +250,7 @@ static void test_find(void) {
 
   for (i = 0; i < tbl.num_ents; i++) {
     int expect = 9999 - i;
-    sprintf(buffer, "%d", expect);
+    gpr_ltoa(expect, buffer);
 
     r = find_simple(&tbl, "test", buffer);
     GPR_ASSERT(r.index == i + 1 + GRPC_CHTTP2_LAST_STATIC_ENTRY);

test/core/transport/chttp2/stream_encoder_test.c

@@ -186,7 +186,7 @@ static void encode_int_to_str(int i, char *p) {
 static void test_decode_table_overflow(void) {
   int i;
   char key[3], value[3];
-  char expect[128];
+  char *expect;
 
   for (i = 0; i < 114; i++) {
     if (i > 0) {
@@ -197,18 +197,21 @@ static void test_decode_table_overflow(void) {
     encode_int_to_str(i + 1, value);
 
     if (i + 61 >= 127) {
-      sprintf(expect, "000009 0104 deadbeef ff%02x 40 02%02x%02x 02%02x%02x",
+      gpr_asprintf(&expect,
+                   "000009 0104 deadbeef ff%02x 40 02%02x%02x 02%02x%02x",
                    i + 61 - 127, key[0], key[1], value[0], value[1]);
     } else if (i > 0) {
-      sprintf(expect, "000008 0104 deadbeef %02x 40 02%02x%02x 02%02x%02x",
+      gpr_asprintf(&expect,
+                   "000008 0104 deadbeef %02x 40 02%02x%02x 02%02x%02x",
                    0x80 + 61 + i, key[0], key[1], value[0], value[1]);
     } else {
-      sprintf(expect, "000007 0104 deadbeef 40 02%02x%02x 02%02x%02x", key[0],
-              key[1], value[0], value[1]);
+      gpr_asprintf(&expect, "000007 0104 deadbeef 40 02%02x%02x 02%02x%02x",
+                   key[0], key[1], value[0], value[1]);
     }
 
     add_sopb_header(key, value);
     verify_sopb(0, 0, 0, expect);
+    gpr_free(expect);
   }
 
   /* if the above passes, then we must have just knocked this pair out of the

test/core/transport/chttp2/timeout_encoding_test.c

@@ -36,6 +36,8 @@
 #include <stdio.h>
 #include <string.h>
 
+#include "src/core/support/string.h"
+#include <grpc/support/alloc.h>
 #include <grpc/support/log.h>
 #include <grpc/support/useful.h>
 #include "test/core/util/test_config.h"
@@ -93,16 +95,23 @@ void decode_suite(char ext, gpr_timespec (*answer)(long x)) {
                       1234567, 12345678, 123456789, 98765432, 9876543, 987654,
                       98765,   9876,     987,       98,       9};
   int i;
-  char input[32];
+  char *input;
   for (i = 0; i < GPR_ARRAY_SIZE(test_vals); i++) {
-    sprintf(input, "%ld%c", test_vals[i], ext);
+    gpr_asprintf(&input, "%ld%c", test_vals[i], ext);
     assert_decodes_as(input, answer(test_vals[i]));
-    sprintf(input, "   %ld%c", test_vals[i], ext);
+    gpr_free(input);
+
+    gpr_asprintf(&input, "   %ld%c", test_vals[i], ext);
     assert_decodes_as(input, answer(test_vals[i]));
-    sprintf(input, "%ld %c", test_vals[i], ext);
+    gpr_free(input);
+
+    gpr_asprintf(&input, "%ld %c", test_vals[i], ext);
     assert_decodes_as(input, answer(test_vals[i]));
-    sprintf(input, "%ld %c  ", test_vals[i], ext);
+    gpr_free(input);
+
+    gpr_asprintf(&input, "%ld %c  ", test_vals[i], ext);
     assert_decodes_as(input, answer(test_vals[i]));
+    gpr_free(input);
   }
 }
 

test/core/transport/metadata_test.c

@@ -35,6 +35,7 @@
 
 #include <stdio.h>
 
+#include "src/core/support/string.h"
 #include "src/core/transport/chttp2/bin_encoder.h"
 #include <grpc/support/alloc.h>
 #include <grpc/support/log.h>
@@ -99,7 +100,7 @@ static void test_create_metadata(void) {
 
 static void test_create_many_ephemeral_metadata(void) {
   grpc_mdctx *ctx;
-  char buffer[256];
+  char buffer[GPR_LTOA_MIN_BUFSIZE];
   long i;
   size_t mdtab_capacity_before;
 
@@ -109,7 +110,7 @@ static void test_create_many_ephemeral_metadata(void) {
   mdtab_capacity_before = grpc_mdctx_get_mdtab_capacity_test_only(ctx);
   /* add, and immediately delete a bunch of different elements */
   for (i = 0; i < MANY; i++) {
-    sprintf(buffer, "%ld", i);
+    gpr_ltoa(i, buffer);
     grpc_mdelem_unref(grpc_mdelem_from_strings(ctx, "a", buffer));
   }
   /* capacity should not grow */
@@ -120,7 +121,7 @@ static void test_create_many_ephemeral_metadata(void) {
 
 static void test_create_many_persistant_metadata(void) {
   grpc_mdctx *ctx;
-  char buffer[256];
+  char buffer[GPR_LTOA_MIN_BUFSIZE];
   long i;
   grpc_mdelem **created = gpr_malloc(sizeof(grpc_mdelem *) * MANY);
   grpc_mdelem *md;
@@ -130,12 +131,12 @@ static void test_create_many_persistant_metadata(void) {
   ctx = grpc_mdctx_create();
   /* add phase */
   for (i = 0; i < MANY; i++) {
-    sprintf(buffer, "%ld", i);
+    gpr_ltoa(i, buffer);
     created[i] = grpc_mdelem_from_strings(ctx, "a", buffer);
   }
   /* verify phase */
   for (i = 0; i < MANY; i++) {
-    sprintf(buffer, "%ld", i);
+    gpr_ltoa(i, buffer);
     md = grpc_mdelem_from_strings(ctx, "a", buffer);
     GPR_ASSERT(md == created[i]);
     grpc_mdelem_unref(md);
@@ -176,7 +177,7 @@ static void test_spin_creating_the_same_thing(void) {
 static void test_things_stick_around(void) {
   grpc_mdctx *ctx;
   int i, j;
-  char buffer[64];
+  char *buffer;
   int nstrs = 10000;
   grpc_mdstr **strs = gpr_malloc(sizeof(grpc_mdstr *) * nstrs);
   int *shuf = gpr_malloc(sizeof(int) * nstrs);
@@ -187,9 +188,10 @@ static void test_things_stick_around(void) {
   ctx = grpc_mdctx_create();
 
   for (i = 0; i < nstrs; i++) {
-    sprintf(buffer, "xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx%dx", i);
+    gpr_asprintf(&buffer, "xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx%dx", i);
     strs[i] = grpc_mdstr_from_string(ctx, buffer);
     shuf[i] = i;
+    gpr_free(buffer);
   }
 
   for (i = 0; i < nstrs; i++) {
@@ -208,10 +210,11 @@ static void test_things_stick_around(void) {
   for (i = 0; i < nstrs; i++) {
     grpc_mdstr_unref(strs[shuf[i]]);
     for (j = i + 1; j < nstrs; j++) {
-      sprintf(buffer, "xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx%dx", shuf[j]);
+      gpr_asprintf(&buffer, "xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx%dx", shuf[j]);
       test = grpc_mdstr_from_string(ctx, buffer);
       GPR_ASSERT(test == strs[shuf[j]]);
       grpc_mdstr_unref(test);
+      gpr_free(buffer);
     }
   }