From c5012d9f73b80bb55ddba2a8785d5c5841e268ec Mon Sep 17 00:00:00 2001
From: Dirk Zimoch <dirk.zimoch@psi.ch>
Date: Fri, 17 Dec 2021 09:16:31 +0100
Subject: [PATCH] Make sure epicsInt8 is signed on all architectures

---
 documentation/RELEASE_NOTES.md       | 11 +++++++++++
 modules/ca/src/client/comBuf.h       |  6 ++++++
 modules/ca/src/client/comQueRecv.cpp |  2 +-
 modules/ca/src/client/comQueRecv.h   |  2 +-
 modules/libcom/src/misc/epicsTypes.h |  2 +-
 5 files changed, 20 insertions(+), 3 deletions(-)

diff --git a/documentation/RELEASE_NOTES.md b/documentation/RELEASE_NOTES.md
index fb925c716..c9f1c69b6 100644
--- a/documentation/RELEASE_NOTES.md
+++ b/documentation/RELEASE_NOTES.md
@@ -16,6 +16,17 @@ should also be read to understand what has changed since earlier releases.
 
 <!-- Insert new items immediately below here ... -->
 
+### Make sure epicsInt8 is signed on all architectures
+
+So far, `epicsInt8` and thus `DBF_CHAR` used to be unsigned on architectures
+where `char` is unsigned, for example on many PPC architectures.
+This had led to different behavior between architectures when converting
+`DBF_CHAR` to signed integer or to floating point types.
+
+WARNING: This fix may change behavior of existing databases on on architectures
+with unsigned `char` (many PPC) when using input links to read from `CHAR`
+waveforms. Architectures with signed `char` (usually x86) are unaffected.
+
 ### Fix for `undefined` in configure/RELEASE files
 
 Prevents `Use of uninitialized value` warnings from convertRelease.pl.
diff --git a/modules/ca/src/client/comBuf.h b/modules/ca/src/client/comBuf.h
index 6a4899414..3d5f58c45 100644
--- a/modules/ca/src/client/comBuf.h
+++ b/modules/ca/src/client/comBuf.h
@@ -88,6 +88,7 @@ public:
     bool push ( const T & value );
     template < class T >
     unsigned push ( const T * pValue, unsigned nElem );
+    unsigned push ( const char * pValue, unsigned nElem );
     unsigned push ( const epicsInt8 * pValue, unsigned nElem );
     unsigned push ( const epicsUInt8 * pValue, unsigned nElem );
     unsigned push ( const epicsOldString * pValue, unsigned nElem );
@@ -208,6 +209,11 @@ inline unsigned comBuf :: push ( const epicsUInt8 *pValue, unsigned nElem )
     return copyInBytes ( pValue, nElem );
 }
 
+inline unsigned comBuf :: push ( const char *pValue, unsigned nElem )
+{
+    return copyInBytes ( pValue, nElem );
+}
+
 inline unsigned comBuf :: push ( const epicsOldString * pValue, unsigned nElem )
 {
     unsigned index = this->nextWriteIndex;
diff --git a/modules/ca/src/client/comQueRecv.cpp b/modules/ca/src/client/comQueRecv.cpp
index 60e142a35..d7d07361b 100644
--- a/modules/ca/src/client/comQueRecv.cpp
+++ b/modules/ca/src/client/comQueRecv.cpp
@@ -46,7 +46,7 @@ void comQueRecv::clear ()
     this->nBytesPending = 0u;
 }
 
-unsigned comQueRecv::copyOutBytes ( epicsInt8 *pBuf, unsigned nBytes )
+unsigned comQueRecv::copyOutBytes ( char *pBuf, unsigned nBytes )
 {
     unsigned totalBytes = 0u;
     do {
diff --git a/modules/ca/src/client/comQueRecv.h b/modules/ca/src/client/comQueRecv.h
index ad8bead88..01c961e51 100644
--- a/modules/ca/src/client/comQueRecv.h
+++ b/modules/ca/src/client/comQueRecv.h
@@ -33,7 +33,7 @@ public:
     comQueRecv ( comBufMemoryManager & );
     ~comQueRecv ();
     unsigned occupiedBytes () const;
-    unsigned copyOutBytes ( epicsInt8 *pBuf, unsigned nBytes );
+    unsigned copyOutBytes ( char *pBuf, unsigned nBytes );
     unsigned removeBytes ( unsigned nBytes );
     void pushLastComBufReceived ( comBuf & );
     void clear ();
diff --git a/modules/libcom/src/misc/epicsTypes.h b/modules/libcom/src/misc/epicsTypes.h
index 432c8961c..5efd69464 100644
--- a/modules/libcom/src/misc/epicsTypes.h
+++ b/modules/libcom/src/misc/epicsTypes.h
@@ -41,7 +41,7 @@ typedef enum {
  * These are sufficient for all our current archs
  * @{
  */
-typedef char            epicsInt8;
+typedef signed char     epicsInt8;
 typedef unsigned char   epicsUInt8;
 typedef short           epicsInt16;
 typedef unsigned short  epicsUInt16;