[PATCH 3 of 4] Postpone filter: fixed incorrect content length check

[Maxim Dounin]

# HG changeset patch
# User Maxim Dounin <mdounin at mdounin.ru>
# Date 1748666373 -10800
#      Sat May 31 07:39:33 2025 +0300
# Node ID 41e7de4b8d3918a501dc95c8b0e706703675fc92
# Parent  1ce7a2381e6a880636779800499a0bf99ca7bd6e
Postpone filter: fixed incorrect content length check.

The code in ngx_http_postpone_filter_in_memory() used to assign
r->headers_out.content_length_n to a size_t variable before comparison,
which can lead to incorrect results on 32-bit platforms.

Fix is to compare r->headers_out.content_length_n before conversion
to size_t.

Found with MSVC with C4244 warnings (conversion from 'type1' to 'type2',
possible loss of data) enabled.

diff --git a/src/http/ngx_http_postpone_filter_module.c b/src/http/ngx_http_postpone_filter_module.c
--- a/src/http/ngx_http_postpone_filter_module.c
+++ b/src/http/ngx_http_postpone_filter_module.c
@@ -194,14 +194,18 @@ ngx_http_postpone_filter_in_memory(ngx_h
         clcf = ngx_http_get_module_loc_conf(r, ngx_http_core_module);
 
         if (r->headers_out.content_length_n != -1) {
-            len = r->headers_out.content_length_n;
 
-            if (len > clcf->subrequest_output_buffer_size) {
+            if (r->headers_out.content_length_n
+                > (off_t) clcf->subrequest_output_buffer_size)
+            {
                 ngx_log_error(NGX_LOG_ERR, c->log, 0,
-                              "too big subrequest response: %uz", len);
+                              "too big subrequest response: %O",
+                              r->headers_out.content_length_n);
                 return NGX_ERROR;
             }
 
+            len = (size_t) r->headers_out.content_length_n;
+
         } else {
             len = clcf->subrequest_output_buffer_size;
         }