Refinement per @vtjnash comments.

Make uv_write() a function (was a macro) and do c_free in "finally" clause.

Explicit null-termination in jl_safe_printf() to allow for win32's
non-posix vsnprintf behaviour. See also JuliaLang#9624.

Use jl_safe_printf() in profile thread.

Send help message to jl_printf(JL_STDOUT,)  was stderr.

base/stream.jl

@@ -725,26 +725,27 @@ end
 #    finish_read(state...)
 #end
 
-macro uv_write(stream, data, len)
-    esc(quote
-        check_open(s)
-        uvw = c_malloc(_sizeof_uv_write)
+function uv_write(s::AsyncStream, p, n::Integer)
+    check_open(s)
+    uvw = c_malloc(_sizeof_uv_write)
+    try
         uv_req_set_data(uvw,C_NULL)
         err = ccall(:jl_uv_write,
                     Int32,
                     (Ptr{Void}, Ptr{Void}, UInt, Ptr{Void}, Ptr{Void}),
-                    handle($(stream)), $(data), $(len), uvw,
+                    handle(s), p, n, uvw,
                     uv_jl_writecb_task::Ptr{Void})
         if err < 0
-            c_free(uvw)
             uv_error("write", err)
         end
         ct = current_task()
         uv_req_set_data(uvw,ct)
         ct.state = :waiting
         stream_wait(ct)
+    finally
         c_free(uvw)
-    end)
+    end
+    return n
 end
 
 ## low-level calls ##
@@ -754,17 +755,14 @@ write(s::AsyncStream, c::Char) = write(s, string(c))
 function write{T}(s::AsyncStream, a::Array{T})
     if isbits(T)
         n = uint(length(a)*sizeof(T))
-        @uv_write s a n
-        return int(n)
+        return uv_write(s, a, n);
     else
         check_open(s)
         invoke(write,(IO,Array),s,a)
     end
 end
-function write(s::AsyncStream, p::Ptr, n::Integer)
-    @uv_write s p n
-    return int(n)
-end
+
+write(s::AsyncStream, p::Ptr, n::Integer) = uv_write(s, p, n)
 
 function _uv_hook_writecb_task(s::AsyncStream,req::Ptr{Void},status::Int32)
     d = uv_req_data(req)

src/jl_uv.c

@@ -605,13 +605,15 @@ int jl_printf(uv_stream_t *s, const char *format, ...)
 DLLEXPORT void jl_safe_printf(const char *fmt, ...)
 {
     static char buf[1000];
+    buf[0] = '\0';
 
     va_list args;
     va_start(args, fmt);
     // Not async signal safe on some platforms?
     vsnprintf(buf, sizeof(buf), fmt, args);
     va_end(args);
 
+    buf[999] = '\0';
     write(STDERR_FILENO, buf, strlen(buf));
 }
 

src/profile.c

@@ -218,7 +218,7 @@ void *mach_profile_listener(void *arg)
                 bt_size_cur += rec_backtrace_ctx_dwarf((ptrint_t*)bt_data_prof+bt_size_cur, bt_size_max-bt_size_cur-1, &uc);
             }
             else if (forceDwarf == -1) {
-                jl_printf(JL_STDERR, "Warning: Profiler attempt to access an invalid memory location\n");
+                jl_safe_printf("Warning: Profiler attempt to access an invalid memory location\n");
             }
 
             forceDwarf = -2;

src/task.c

@@ -702,7 +702,7 @@ DLLEXPORT void gdblookup(ptrint_t ip)
         if (line_num == ip)
             jl_safe_printf("unknown function (ip: %d)\n", line_num);
         else if (line_num == -1)
-            jl_safe_printf("%s at %s (unknown line)\n", func_name, file_name, line_num);
+            jl_safe_printf("%s at %s (unknown line)\n", func_name, file_name);
         else
             jl_safe_printf("%s at %s:%d\n", func_name, file_name, line_num);
     }

ui/repl.c

@@ -139,7 +139,7 @@ void parse_opts(int *argcp, char ***argvp)
             jl_compileropts.cpu_target = strdup(optarg);
             break;
         case 'h':
-            jl_printf(JL_STDERR, "%s%s", usage, opts);
+            jl_printf(JL_STDOUT, "%s%s", usage, opts);
             jl_exit(0);
         case 'O':
             jl_compileropts.opt_level = 1;