git/list[1] front-page[2] threads[3] people[4] search[5] about
 

[PATCH 1/2] Revert "vreportf: avoid intermediate buffer"

From
Jeff King <peff@peff.net>
Date
Jan 11, 2017, 14:02 UTC
Message-ID
<20170111140203.obhd2t6yorszex73@sigill.intra.peff.net>
In-Reply-To
<20170111140138.5p647xuqpqrej63b@sigill.intra.peff.net>
This reverts commit f4c3edc0b156362a92bf9de4f0ec794e90a757fc.

The purpose of that commit was to let us write errors of arbitrary length to stderr by skipping the intermediate buffer and sending our varargs straight to fprintf. That works, but it comes with a downside: we do not get access to the varargs before they are sent to stderr.

On balance, it's not a good tradeoff. Error messages larger than our 4K buffer are quite uncommon, and we've lost the ability to make any modifications to the output (e.g., to remove non-printable characters).

The only way to have both would be one of:
  1. Write into a dynamic buffer. But this is a bad idea for
     a low-level function that may be called when malloc()
     has failed.
  2. Do our own printf-format varargs parsing. This is too
     complex to be worth the trouble.
Let's just revert that change and go back to a fixed buffer.
Signed-off-by: Jeff King <peff@peff.net>
---
 usage.c | 15 +++------------
 1 file changed, 3 insertions(+), 12 deletions(-)
diff --git a/usage.c b/usage.c
index 17f52c1b5..b1cbe6799 100644
--- a/usage.c
+++ b/usage.c
@@ -7,21 +7,13 @@
 #include "cache.h"
 
 static FILE *error_handle;
-static int tweaked_error_buffering;
 
 void vreportf(const char *prefix, const char *err, va_list params)
 {
+	char msg[4096];
 	FILE *fh = error_handle ? error_handle : stderr;
-
-	fflush(fh);
-	if (!tweaked_error_buffering) {
-		setvbuf(fh, NULL, _IOLBF, 0);
-		tweaked_error_buffering = 1;
-	}
-
-	fputs(prefix, fh);
-	vfprintf(fh, err, params);
-	fputc('\n', fh);
+	vsnprintf(msg, sizeof(msg), err, params);
+	fprintf(fh, "%s%s\n", prefix, msg);
 }
 
 static NORETURN void usage_builtin(const char *err, va_list params)
@@ -93,7 +85,6 @@ void set_die_is_recursing_routine(int (*routine)(void))
 void set_error_handle(FILE *fh)
 {
 	error_handle = fh;
-	tweaked_error_buffering = 0;
 }
 
 void NORETURN usagef(const char *err, ...)
-- 
2.11.0.627.gfa6151259
Previous: Jeff KingNext: Jeff King
Message 2 of 6 in “sanitizing error message contents”
  1. 0/2 sanitizing error message contentsJeff King, Jan 11, 2017
  2. 1/2 Revert "vreportf: avoid intermediate buffer"Jeff King, Jan 11, 2017
  3. 2/2 vreport: sanitize ASCII control charsJeff King, Jan 11, 2017
  4. 3/2 vreportf: add prefix to each lineJeff King, Jan 11, 2017
  5. Junio C HamanoJan 11, 2017
  6. Jeff KingJan 12, 2017

Read the whole thread, see it on lore, or plain text.

$ cat FOOTERMessages come from the public archive at lore.kernel.org/git, fetched every hour. The front page is chosen and written each morning by an AI editor and can be wrong; the threads themselves are the record. About and API. For agents: an MCP server at https://gitlist.dev/mcp, and any thread, story or person page as Markdown by adding .md to its URL (or sending Accept: text/markdown). Details in /llms.txt.