From 307d911078e9c5f8932de09c3991ca909a836e91 Mon Sep 17 00:00:00 2001
From: Masayuki Yamamoto <15698961+ma8ma@users.noreply.github.com>
Date: Sat, 23 Sep 2023 21:51:16 +0900
Subject: [PATCH] Reset errno to zero before calling functions (#1256)
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関数を呼び出した後にerrnoの値をチェックする箇所では関数を呼び出す前に
errnoを0にリセットします。

参考文献
- https://linuxjm.osdn.jp/html/LDP_man-pages/man3/errno.3.html
- https://www.jpcert.or.jp/sc-rules/c-err30-c.html
---
 src/iomonitor.cpp           |  2 ++
 src/jdlib/jdiconv.cpp       |  2 ++
 src/jdlib/jdsocket.cpp      | 11 +++++++++--
 src/jdlib/jdsocketopenssl.h |  1 +
 4 files changed, 14 insertions(+), 2 deletions(-)

diff --git a/src/iomonitor.cpp b/src/iomonitor.cpp
index 457646cd5..f7a2b2c7b 100644
--- a/src/iomonitor.cpp
+++ b/src/iomonitor.cpp
@@ -64,6 +64,7 @@ void IOMonitor::init_connection()
     int mkfifo_status = -1;
 
     do_makefifo:
+    errno = 0;
     mkfifo_status = mkfifo( m_fifo_file.c_str(), O_RDWR | S_IRUSR | S_IWUSR );
 
     // FIFO作成でエラーになった( 基本的に既にメインプロセスがある )
@@ -73,6 +74,7 @@ void IOMonitor::init_connection()
         if( errno == EEXIST )
         {
             // FIFOを書き込み専用モードでオープン( ノンブロック )
+            errno = 0;
             if( ( m_fifo_fd = open( m_fifo_file.c_str(), O_WRONLY | O_NONBLOCK ) ) == -1 )
             {
                 // 反対側が既にオープンされていない( 異常終了などでメインプロセスがない )
diff --git a/src/jdlib/jdiconv.cpp b/src/jdlib/jdiconv.cpp
index 068130ef5..0905d8cea 100644
--- a/src/jdlib/jdiconv.cpp
+++ b/src/jdlib/jdiconv.cpp
@@ -58,6 +58,7 @@ Iconv::Iconv( const Encoding to, const Encoding from, const bool broken_sjis_be_
 void Iconv::open_by_alternative_names( const char* to_str, const char* from_str )
 {
     // "MS932"で失敗したら"CP932"で試してみる
+    errno = 0;
     if( m_enc_to == Encoding::sjis ) m_cd = g_iconv_open( "CP932", from_str );
     else if( m_enc_from == Encoding::sjis ) m_cd = g_iconv_open( to_str, "CP932" );
 
@@ -150,6 +151,7 @@ std::string& Iconv::convert( char* str_in, std::size_t size_in, std::string& out
         std::size_t byte_left_in = buf_in_end - buf_in_tmp;
         std::size_t byte_left_out = buf_out_end - buf_out_tmp;
 
+        errno = 0;
         const int ret = g_iconv( m_cd, &buf_in_tmp, &byte_left_in, &buf_out_tmp, &byte_left_out );
 
 #ifdef _DEBUG
diff --git a/src/jdlib/jdsocket.cpp b/src/jdlib/jdsocket.cpp
index 46ead6122..629a3a375 100644
--- a/src/jdlib/jdsocket.cpp
+++ b/src/jdlib/jdsocket.cpp
@@ -163,6 +163,7 @@ bool Socket::connect( const std::string& hostname, const std::string& port, cons
     }
 
     // connect peer
+    errno = 0;
     err = ::connect( m_soc, ainf->ai_addr, ainf->ai_addrlen );
     if( err ) {
         // ノンブロックでまだ接続中
@@ -375,19 +376,24 @@ int Socket::write( const char* buf, const std::size_t bufsize )
                 return kSocket_ERR;
             }
 
+            int err;
 #ifdef MSG_NOSIGNAL
+            errno = 0;
             tmpsize = ::send( m_soc, buf + bufsize - send_size, send_size, MSG_NOSIGNAL );
+            err = errno;
 #else
             // SolarisにはMSG_NOSIGNALが無いのでSIGPIPEをIGNOREする (FreeBSD4.11Rにもなかった)
             signal( SIGPIPE, SIG_IGN ); /* シグナルを無視する */
+            errno = 0;
             tmpsize = ::send( m_soc, buf + bufsize - send_size, send_size, 0 );
+            err = errno;
             signal( SIGPIPE, SIG_DFL ); /* 念のため戻す */
 #endif // MSG_NOSIGNAL
 
             if( tmpsize == 0
-                || ( tmpsize < 0 && !( errno == EAGAIN || errno == EWOULDBLOCK || errno == EINTR ) ) )
+                || ( tmpsize < 0 && !( err == EAGAIN || err == EWOULDBLOCK || err == EINTR ) ) )
             {
-                m_errmsg = std::string{ "send failed: errno=" } + std::strerror( errno );
+                m_errmsg = std::string{ "send failed: errno=" } + std::strerror( err );
                 return kSocket_ERR;
             }
         }
@@ -432,6 +438,7 @@ int Socket::read( char* buf, const std::size_t bufsize )
                 return kSocket_ERR;
             }
 
+            errno = 0;
             ret = ::recv( m_soc, buf, bufsize, 0 );
             if( ret < 0 && !( errno == EAGAIN || errno == EWOULDBLOCK || errno == EINTR ) ) {
 
diff --git a/src/jdlib/jdsocketopenssl.h b/src/jdlib/jdsocketopenssl.h
index b16059d2d..508cf8d31 100644
--- a/src/jdlib/jdsocketopenssl.h
+++ b/src/jdlib/jdsocketopenssl.h
@@ -149,6 +149,7 @@ void Socket::tls_close()
 {
     int ret;
 
+    errno = 0;
     while( ( ret = SSL_shutdown( m_tls ) ) != 1 ) {
         WaitFor want_read = WaitFor::recv;