Erroring on strict-overflow is a little too strict, GCC 4.9 is smart

2 files changed, 25 insertions, 29 deletions

diff --git a/src/build-data/cc/gcc.txt b/src/build-data/cc/gcc.txt
index 365ec87f9..2aff1bf6b 100644
--- a/src/build-data/cc/gcc.txt
+++ b/src/build-data/cc/gcc.txt
@@ -8,8 +8,8 @@ add_include_dir_option -I
 add_lib_dir_option -L
 add_lib_option -l
 
-lang_flags "-std=c++11 -D_REENTRANT -fstack-protector"
-maintainer_warning_flags "-Werror -Wno-error=old-style-cast -Wno-error=zero-as-null-pointer-constant -Wno-error=unused-parameter -Wno-error=unused-variable"
+lang_flags "-std=c++11 -D_REENTRANT -D_FORTIFY_SOURCE=2 -fstack-protector"
+maintainer_warning_flags "-Werror -Wno-error=old-style-cast -Wno-error=zero-as-null-pointer-constant -Wno-error=unused-parameter -Wno-error=unused-variable -Wno-error=strict-overflow"
 warning_flags "-Wall -Wextra -Wstrict-aliasing -Wstrict-overflow=5 -Wcast-align -Wmissing-declarations -Wpointer-arith -Wcast-qual -Wold-style-cast -Wzero-as-null-pointer-constant"
 
 lib_opt_flags "-O3"
@@ -26,28 +26,27 @@ makefile_style gmake
 # The default works for GNU ld and several other Unix linkers
 default -> "$(CXX) -shared -fPIC -Wl,-soname,$(SONAME)"
 
-# AIX doesn't seem to have soname support (weird...)
-aix     -> "$(CXX) -shared -fPIC"
-
-# OpenBSD doesn't use soname
-openbsd -> "$(CXX) -shared -fPIC"
-
+# Darwin, HP-UX and Solaris linkers use different syntax
 darwin  -> "$(CXX) -dynamiclib -fPIC -install_name $(LIBDIR)/$(SONAME)"
 hpux    -> "$(CXX) -shared -fPIC -Wl,+h,$(SONAME)"
 solaris -> "$(CXX) -shared -fPIC -Wl,-h,$(SONAME)"
+
+# AIX and OpenBSD don't use sonames at all
+aix     -> "$(CXX) -shared -fPIC"
+openbsd -> "$(CXX) -shared -fPIC"
 </so_link_flags>
 
 <isa_flags>
-sse2   -> "-msse2"
-ssse3  -> "-mssse3"
-sse4.1 -> "-msse4.1"
-sse4.2 -> "-msse4.2"
-avx2   -> "-mavx2"
-bmi2   -> "-mbmi2"
-aesni  -> "-maes"
-clmul  -> "-mpclmul"
-rdrand -> "-mrdrnd"
-sha    -> "-msha"
+sse2    -> "-msse2"
+ssse3   -> "-mssse3"
+sse4.1  -> "-msse4.1"
+sse4.2  -> "-msse4.2"
+avx2    -> "-mavx2"
+bmi2    -> "-mbmi2"
+aesni   -> "-maes"
+clmul   -> "-mpclmul"
+rdrand  -> "-mrdrnd"
+sha     -> "-msha"
 altivec -> "-maltivec"
 </isa_flags>
 
diff --git a/src/lib/modes/cbc/cbc.cpp b/src/lib/modes/cbc/cbc.cpp
index 3095875f5..5fe5c8b17 100644
--- a/src/lib/modes/cbc/cbc.cpp
+++ b/src/lib/modes/cbc/cbc.cpp
@@ -99,15 +99,15 @@ void CBC_Encryption::update(secure_vector<byte>& buffer, size_t offset)
    BOTAN_ASSERT(sz % BS == 0, "CBC input is full blocks");
    const size_t blocks = sz / BS;
 
+   const byte* prev_block = state_ptr();
+
    if(blocks)
       {
-      xor_buf(&buf[0], state_ptr(), BS);
-      cipher().encrypt(&buf[0]);
-
-      for(size_t i = 1; i != blocks; ++i)
+      for(size_t i = 0; i != blocks; ++i)
          {
-         xor_buf(&buf[BS*i], &buf[BS*(i-1)], BS);
+         xor_buf(&buf[BS*i], prev_block, BS);
          cipher().encrypt(&buf[BS*i]);
+         prev_block = &buf[BS*i];
          }
 
       state().assign(&buf[BS*(blocks-1)], &buf[BS*blocks]);
@@ -267,6 +267,7 @@ void CTS_Decryption::finish(secure_vector<byte>& buffer, size_t offset)
    if(sz % BS == 0)
       {
       // swap last two blocks
+
       for(size_t i = 0; i != BS; ++i)
          std::swap(buffer[buffer.size()-BS+i], buffer[buffer.size()-2*BS+i]);
 
@@ -283,21 +284,17 @@ void CTS_Decryption::finish(secure_vector<byte>& buffer, size_t offset)
       update(buffer, offset);
 
       cipher().decrypt(&last[0]);
+
       xor_buf(&last[0], &last[BS], final_bytes - BS);
 
       for(size_t i = 0; i != final_bytes - BS; ++i)
-         {
-         last[i] ^= last[i + BS];
-         last[i + BS] ^= last[i];
-         last[i] ^= last[i + BS];
-         }
+         std::swap(last[i], last[i + BS]);
 
       cipher().decrypt(&last[0]);
       xor_buf(&last[0], state_ptr(), BS);
 
       buffer += last;
       }
-
    }
 
 }