From bd57e2b43a5b56c00a82adbde0e33e5820c81164 Mon Sep 17 00:00:00 2001 From: Rich Felker Date: Mon, 4 Apr 2011 16:24:49 -0400 Subject: [PATCH] use a local temp buffer for unbuffered streams in vfprintf this change makes it so most calls to fprintf(stderr, ...) will result in a single writev syscall, as opposed to roughly 2*N syscalls (and possibly more) where N is the number of format specifiers. in principle we could use a much larger buffer, but it's best not to increase the stack requirements too much. most messages are under 80 chars. --- src/stdio/stderr.c | 1 + src/stdio/vfprintf.c | 13 +++++++++++++ 2 files changed, 14 insertions(+) diff --git a/src/stdio/stderr.c b/src/stdio/stderr.c index 3bdaffbc..9a70700c 100644 --- a/src/stdio/stderr.c +++ b/src/stdio/stderr.c @@ -6,6 +6,7 @@ static FILE f = { .buf_size = 0, .fd = 2, .flags = F_PERM | F_NORD, + .lbf = -1, .write = __stdio_write, .seek = __stdio_seek, .close = __stdio_close, diff --git a/src/stdio/vfprintf.c b/src/stdio/vfprintf.c index 57878c03..8cbfd96e 100644 --- a/src/stdio/vfprintf.c +++ b/src/stdio/vfprintf.c @@ -627,13 +627,26 @@ int vfprintf(FILE *f, const char *fmt, va_list ap) va_list ap2; int nl_type[NL_ARGMAX] = {0}; union arg nl_arg[NL_ARGMAX]; + unsigned char internal_buf[80], *saved_buf = 0; int ret; va_copy(ap2, ap); if (printf_core(0, fmt, &ap2, nl_arg, nl_type) < 0) return -1; FLOCK(f); + if (!f->buf_size) { + saved_buf = f->buf; + f->buf = internal_buf; + f->buf_size = sizeof internal_buf; + } ret = printf_core(f, fmt, &ap2, nl_arg, nl_type); + if (saved_buf) { + f->write(f, 0, 0); + if (!f->wpos) ret = -1; + f->buf = saved_buf; + f->buf_size = 0; + f->wpos = f->wbase = f->wend = 0; + } FUNLOCK(f); va_end(ap2); return ret; -- 2.25.1