TTreeCache::FillBuffer Updates

[pcanal]

This fixes the problem described in http://root-forum.cern.ch/t/ttreecache-fillbuffer-error-with-root-6-14-04/30914/1 (And avoid the same error message in another circumstance).

[phsft-bot]

Starting build on slc6/gcc48, slc6-i686/gcc49, centos7/clang39, centos7/gcc62, centos7/gcc7, fedora28/native, ubuntu16/native, mac1013/native, windows10/vc15 with flags -Dccache=ON
How to customize builds

[phsft-bot]

Build failed on fedora28/native.
See console output.

Warnings:

• /mnt/build/workspace/root-pullrequests-build/root/core/meta/src/TClass.cxx:686:14: warning: ‘char* strncpy(char*, const char*, size_t)’ specified bound depends on the length of the source argument [-Wstringop-overflow=]
• /mnt/build/workspace/root-pullrequests-build/root/net/rpdutils/src/rpdutils.cxx:5203:14: warning: ‘char* strncpy(char*, const char*, size_t)’ specified bound depends on the length of the source argument [-Wstringop-overflow=]
• /mnt/build/workspace/root-pullrequests-build/root/net/rpdutils/src/rpdutils.cxx:4757:26: warning: ‘char* strncpy(char*, const char*, size_t)’ output may be truncated copying 10 bytes from a string of length 10 [-Wstringop-truncation]
• /mnt/build/workspace/root-pullrequests-build/root/net/rootd/src/rootd.cxx:490:14: warning: ‘char* strncat(char*, const char*, size_t)’ accessing between 2147483648 and 2147483647 bytes at offsets 0 and [-2147483647, 2147483648] may overlap 1 byte at offset [0, 4294967295] [-Wrestrict]
• /mnt/build/workspace/root-pullrequests-build/root/net/rootd/src/rootd.cxx:761:21: warning: ‘%lu’ directive writing between 1 and 20 bytes into a region of size between 0 and 8191 [-Wformat-overflow=]
• /mnt/build/workspace/root-pullrequests-build/root/graf3d/ftgl/src/FTVectoriser.cxx:186:76: warning: cast between incompatible function types from ‘void ()(GLenum, FTMesh)’ {aka ‘void ()(unsigned int, FTMesh)’} to ‘GLUTesselatorFunction’ {aka ‘void (*)()’} [-Wcast-function-type]
• /mnt/build/workspace/root-pullrequests-build/root/graf3d/ftgl/src/FTVectoriser.cxx:187:76: warning: cast between incompatible function types from ‘void ()(void, FTMesh*)’ to ‘GLUTesselatorFunction’ {aka ‘void (*)()’} [-Wcast-function-type]
• /mnt/build/workspace/root-pullrequests-build/root/graf3d/ftgl/src/FTVectoriser.cxx:188:76: warning: cast between incompatible function types from ‘void ()(FTGL_DOUBLE, void**, GLfloat*, void**, FTMesh*)’ {aka ‘void ()(double, void**, float*, void**, FTMesh*)’} to ‘GLUTesselatorFunction’ {aka ‘void (*)()’} [-Wcast-function-type]
• /mnt/build/workspace/root-pullrequests-build/root/graf3d/ftgl/src/FTVectoriser.cxx:189:76: warning: cast between incompatible function types from ‘void ()(FTMesh)’ to ‘GLUTesselatorFunction’ {aka ‘void (*)()’} [-Wcast-function-type]
• /mnt/build/workspace/root-pullrequests-build/root/graf3d/ftgl/src/FTVectoriser.cxx:190:76: warning: cast between incompatible function types from ‘void ()(GLenum, FTMesh)’ {aka ‘void ()(unsigned int, FTMesh)’} to ‘GLUTesselatorFunction’ {aka ‘void (*)()’} [-Wcast-function-type]

And 193 more

Failing tests:

• projectroot.roottest.cling.functionTemplate.roottest_cling_functionTemplate_testcint
• projectroot.roottest.root.multicore.roottest_root_multicore_processExecutorH1Test

[pcanal]

processExecutorH1Test and cling_functionTemplate_testcint fails in the head v6.14 patch branch