From: Daniel Stenberg <daniel@haxx.se>
Date: Fri, 28 Nov 2025 16:16:31 +0000 (+0100)
Subject: memdebug: buffer output data
X-Git-Tag: rc-8_18_0-1~92
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=06e16167d62984976b7a3ea2fcfa61813fd6d81c;p=thirdparty%2Fcurl.git

memdebug: buffer output data

Instead of writing each line to file immediately, this now stores them
in an in-memory buffer until that gets full or curl exits. To make it
run faster and write to file less often.

Closes #19750
---

diff --git a/lib/memdebug.c b/lib/memdebug.c
index 9fd54d026b..329b11ea79 100644
--- a/lib/memdebug.c
+++ b/lib/memdebug.c
@@ -62,6 +62,10 @@ static long memsize = 0;  /* set number of mallocs allowed */
 static struct backtrace_state *btstate;
 #endif
 
+#define KEEPSIZE 10000
+static char membuf[KEEPSIZE];
+static size_t memwidx = 0; /* write index */
+
 /* LeakSantizier (LSAN) calls _exit() instead of exit() when a leak is detected
    on exit so the logfile must be closed explicitly or data could be lost.
    Though _exit() does not call atexit handlers such as this, LSAN's call to
@@ -71,6 +75,8 @@ static void curl_dbg_cleanup(void)
   if(curl_dbg_logfile &&
      curl_dbg_logfile != stderr &&
      curl_dbg_logfile != stdout) {
+    if(memwidx)
+      fwrite(membuf, 1, memwidx, curl_dbg_logfile);
     /* !checksrc! disable BANNEDFUNC 1 */
     fclose(curl_dbg_logfile);
   }
@@ -506,7 +512,7 @@ int curl_dbg_fclose(FILE *file, int line, const char *source)
 void curl_dbg_log(const char *format, ...)
 {
   char buf[1024];
-  int nchars;
+  size_t nchars;
   va_list ap;
 
   if(!curl_dbg_logfile)
@@ -519,8 +525,20 @@ void curl_dbg_log(const char *format, ...)
   if(nchars > (int)sizeof(buf) - 1)
     nchars = (int)sizeof(buf) - 1;
 
-  if(nchars > 0)
-    fwrite(buf, 1, (size_t)nchars, curl_dbg_logfile);
+  if(nchars > 0) {
+    if(KEEPSIZE - nchars < memwidx) {
+      /* flush */
+      fwrite(membuf, 1, memwidx, curl_dbg_logfile);
+      fflush(curl_dbg_logfile);
+      memwidx = 0;
+    }
+    if(memwidx) {
+      /* the previous line ends with a newline */
+      DEBUGASSERT(membuf[memwidx - 1] == '\n');
+    }
+    memcpy(&membuf[memwidx], buf, nchars);
+    memwidx += nchars;
+  }
 }
 
 #endif /* CURLDEBUG */