From 6d81f014764e3bb9452d3697b84093bed0668f02 Mon Sep 17 00:00:00 2001
From: Jay Berkenbilt <ejb@ql.org>
Date: Tue, 17 Sep 2019 12:13:19 -0400
Subject: [PATCH] Don't assume char is signed in int conversion tests (fixes
 #361)

---
 ChangeLog                      |  4 ++++
 include/qpdf/QIntC.hh          |  7 +++++++
 libtests/qintc.cc              | 11 +++++++----
 libtests/qtest/qintc/qintc.out |  4 +++-
 4 files changed, 21 insertions(+), 5 deletions(-)

diff --git a/ChangeLog b/ChangeLog
index 4ec6ea9d..29da54b9 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,7 @@
+2019-09-17  Jay Berkenbilt  <ejb@ql.org>
+
+	* QIntC tests: don't assume char is signed. Fixes #361.
+
 2019-08-31  Jay Berkenbilt  <ejb@ql.org>
 
 	* 9.0.0: release
diff --git a/include/qpdf/QIntC.hh b/include/qpdf/QIntC.hh
index 3383a91c..8a6b74c0 100644
--- a/include/qpdf/QIntC.hh
+++ b/include/qpdf/QIntC.hh
@@ -50,6 +50,13 @@ namespace QIntC // QIntC = qpdf Integer Conversion
         typedef unsigned char type;
     };
 
+    template <>
+    class to_u<signed char>
+    {
+      public:
+        typedef unsigned char type;
+    };
+
     template <>
     class to_u<short>
     {
diff --git a/libtests/qintc.cc b/libtests/qintc.cc
index 53ec3772..6b35e837 100644
--- a/libtests/qintc.cc
+++ b/libtests/qintc.cc
@@ -32,12 +32,13 @@ int main()
     uint64_t ul1 = 1099511627776LL; // Too big for 32-bit
     uint64_t ul2 = 12345;           // Fits into 32-bit
     int32_t i2 = 81;                // Fits in char and uchar
-    char c1 = '\xf7';               // Signed value when char
+    signed char c1 = static_cast<signed char>('\xf7'); // Signed value when char
+    char c2 = 'W';                  // char; may be signed or unsigned
 
     // Verify i1 and u1 have same bit pattern
     assert(static_cast<uint32_t>(i1) == u1);
-    // Verify that we can unsafely convert between char and unsigned char
-    assert(c1 == static_cast<char>(static_cast<unsigned char>(c1)));
+    // Verify that we can unsafely convert between signed and unsigned char
+    assert(c1 == static_cast<signed char>(static_cast<unsigned char>(c1)));
 
     try_convert(true,  QIntC::to_int<int32_t>, i1);
     try_convert(true,  QIntC::to_uint<uint32_t>, u1);
@@ -51,7 +52,9 @@ int main()
     try_convert(false, QIntC::to_ulonglong<int32_t>, i1);
     try_convert(true,  QIntC::to_char<int32_t>, i2);
     try_convert(true,  QIntC::to_uchar<int32_t>, i2);
-    try_convert(false, QIntC::to_uchar<char>, c1);
+    try_convert(false, QIntC::to_uchar<signed char>, c1);
+    try_convert(true,  QIntC::to_uchar<char>, c2);
+    try_convert(true,  QIntC::to_char<char>, c2);
 
     return 0;
 }
diff --git a/libtests/qtest/qintc/qintc.out b/libtests/qtest/qintc/qintc.out
index 5c6479e2..2a2ff9f5 100644
--- a/libtests/qtest/qintc/qintc.out
+++ b/libtests/qtest/qintc/qintc.out
@@ -10,4 +10,6 @@ QIntC::to_offset<int32_t>(i1): -1153374643 -1153374643 PASSED
 QIntC::to_ulonglong<int32_t>(i1): integer out of range converting -1153374643 from a 4-byte signed type to a 8-byte unsigned type PASSED
 QIntC::to_char<int32_t>(i2): 81 Q PASSED
 QIntC::to_uchar<int32_t>(i2): 81 Q PASSED
-QIntC::to_uchar<char>(c1): integer out of range converting ÷ from a 1-byte signed type to a 1-byte unsigned type PASSED
+QIntC::to_uchar<signed char>(c1): integer out of range converting ÷ from a 1-byte signed type to a 1-byte unsigned type PASSED
+QIntC::to_uchar<char>(c2): W W PASSED
+QIntC::to_char<char>(c2): W W PASSED