SSI: fixed incorrect or duplicate stub output. Following 3518:eb3aaf8bd2a9 (0.8.37), r->request_output is only set if there are data in the first buffer sent in the subrequest. As a result, following the change mentioned this flag cannot be used to prevent duplicate ngx_http_ssi_stub_output() calls, since it is not set if there was already some output, but the first buffer was empty. Still, when there are multiple subrequests, even an empty subrequest response might be delayed by the postpone filter, leading to a second call of ngx_http_ssi_stub_output() during finalization from ngx_http_writer() the subreqest buffers are released by the postpone filter. Since r->request_output is not set after the first call, this resulted in duplicate stub output. Additionally, checking only the first buffer might be wrong in some unusual cases. For example, the first buffer might be empty if $r->flush() is called before printing any data in the embedded Perl module. Depending on the postpone_output value and corresponding sizes, this issue can result in either duplicate or unexpected stub output, or "zero size buf in writer" alerts. Following 8124:f5515e727656 (1.23.4), it became slightly easier to reproduce the issue, as empty static files and empty cache items now result in a response with an empty buffer. Before the change, an empty proxied response can be used to reproduce the issue. Fix is check all buffers and set r->request_output if any non-empty buffers are sent. This ensures that all unusual cases of non-empty responses are covered, and also that r->request_output will be set after the first stub output, preventing duplicate output. Reported by Jan Gassen.

# Copyright (C) Igor Sysoev
# Copyright (C) Nginx, Inc.


# Compaq C V6.5-207

ngx_include_opt="-I"

# warnings

CFLAGS="$CFLAGS -msg_enable level6 -msg_fatal level6"

CFLAGS="$CFLAGS -msg_disable unknownmacro"
CFLAGS="$CFLAGS -msg_disable unusedincl"
CFLAGS="$CFLAGS -msg_disable unnecincl"
CFLAGS="$CFLAGS -msg_disable nestincl"
CFLAGS="$CFLAGS -msg_disable strctpadding"
CFLAGS="$CFLAGS -msg_disable ansialiascast"
CFLAGS="$CFLAGS -msg_disable inlinestoclsmod"
CFLAGS="$CFLAGS -msg_disable cxxkeyword"
CFLAGS="$CFLAGS -msg_disable longlongsufx"
CFLAGS="$CFLAGS -msg_disable valuepres"

# STUB
CFLAGS="$CFLAGS -msg_disable truncintcast"
CFLAGS="$CFLAGS -msg_disable trunclongcast"

CFLAGS="$CFLAGS -msg_disable truncintasn"
CFLAGS="$CFLAGS -msg_disable trunclongint"
CFLAGS="$CFLAGS -msg_disable intconcastsgn"
CFLAGS="$CFLAGS -msg_disable intconstsign"
CFLAGS="$CFLAGS -msg_disable switchlong"
CFLAGS="$CFLAGS -msg_disable subscrbounds2"

CFLAGS="$CFLAGS -msg_disable hexoctunsign"

CFLAGS="$CFLAGS -msg_disable ignorecallval"
CFLAGS="$CFLAGS -msg_disable nonstandcast"
CFLAGS="$CFLAGS -msg_disable embedcomment"
CFLAGS="$CFLAGS -msg_disable unreachcode"
CFLAGS="$CFLAGS -msg_disable questcompare2"
CFLAGS="$CFLAGS -msg_disable unusedtop"
CFLAGS="$CFLAGS -msg_disable unrefdecl"

CFLAGS="$CFLAGS -msg_disable bitnotint"