-Wstrict-aliasing warnings

[sanjayankur31]

While building iv for NeuroFedora, we noticed a few -Wstrict-aliasing warnings (grepped from the build logs):

make[2]: Entering directory '/builddir/build/BUILD/iv-74f120781bc2def0cc4d1f9f547c07037e8a7a74/src/lib'
libtool: compile:  gcc -DHAVE_CONFIG_H -I. -I. -I../include -O2 -g -pipe -Wall -Werror=format-security -Wp,-D_FORTIFY_SOURCE=2 -Wp,-D_GLIBCXX_ASSERTIONS -fexceptions -fstack-protector-strong -grecord-gcc-switches -specs=/usr/lib/rpm/redhat/redhat-hardened-cc1 -specs=/usr/lib/rpm/redhat/redhat-annobin-cc1 -m64 -mtune=generic -fasynchronous-unwind-tables -fstack-clash-protection -fcf-protection -DCOLORIMETRY_SUPPORT -DJPEG_SUPPORT -DYCBCR_SUPPORT -DCMYK_SUPPORT -DHAVE_IEEEFP=1 -DUSE_VARARGS=0 -DUSE_PROTOTYPES=1 -DUSE_CONST=1 -I../include/TIFF -c TIFF/tif_dirwrite.c  -fPIC -DPIC -o TIFF/.libs/tif_dirwrite.o
make[2]: Leaving directory '/builddir/build/BUILD/iv-74f120781bc2def0cc4d1f9f547c07037e8a7a74/src/lib'
TIFF/tif_dirwrite.c: In function 'TIFFWriteNormalTag':
TIFF/tif_dirwrite.c:442:24: warning: dereferencing type-punned pointer will break strict-aliasing rules [-Wstrict-aliasing]
  442 |    dir->tdir_offset = *(u_long *)&fv; /* XXX */
      |                        ^~~~~~~~~~~~~
At top level:
TIFF/tif_dirwrite.c:5:13: warning: 'rcsid' defined but not used [-Wunused-variable]
--
make[2]: Leaving directory '/builddir/build/BUILD/iv-74f120781bc2def0cc4d1f9f547c07037e8a7a74/src/lib'
make[2]: Entering directory '/builddir/build/BUILD/iv-74f120781bc2def0cc4d1f9f547c07037e8a7a74/src/lib'
libtool: compile:  g++ -DHAVE_CONFIG_H -I. -I. -I../include -O2 -g -pipe -Wall -Werror=format-security -Wp,-D_FORTIFY_SOURCE=2 -Wp,-D_GLIBCXX_ASSERTIONS -fexceptions -fstack-protector-strong -grecord-gcc-switches -specs=/usr/lib/rpm/redhat/redhat-hardened-cc1 -specs=/usr/lib/rpm/redhat/redhat-annobin-cc1 -m64 -mtune=generic -fasynchronous-unwind-tables -fstack-clash-protection -fcf-protection -c Unidraw/catcmds.cpp  -fPIC -DPIC -o Unidraw/.libs/catcmds.o
Unidraw/catcmds.cpp: In member function 'virtual void ivViewCompCmd::Execute()':
Unidraw/catcmds.cpp:307:51: warning: dereferencing type-punned pointer will break strict-aliasing rules [-Wstrict-aliasing]
  307 |         if (catalog->Retrieve(name, (Component*&) comp)) {
      |                                                   ^~~~
Unidraw/catcmds.cpp: In member function 'virtual void ivPrintCmd::Execute()':
Unidraw/catcmds.cpp:575:27: warning: 'tmpfilename' may be used uninitialized in this function [-Wmaybe-uninitialized]
--
Unidraw/import.cpp:220:10: warning: unused variable 'imported' [-Wunused-variable]
  220 |     bool imported = false;
      |          ^~~~~~~~
Unidraw/import.cpp: In static member function 'static ivGraphicComp* ivImportCmd::Import(const char*)':
Unidraw/import.cpp:260:52: warning: dereferencing type-punned pointer will break strict-aliasing rules [-Wstrict-aliasing]
  260 |         if (catalog->Valid(filename, (Component*&) comp)) {
      |                                                    ^~~~
Unidraw/import.cpp:263:62: warning: dereferencing type-punned pointer will break strict-aliasing rules [-Wstrict-aliasing]
  263 |         } else if (catalog->Retrieve(filename, (Component*&) comp)) {
      |                                                              ^~~~
Unidraw/import.cpp: In static member function 'static ivGraphicComp* ivImportCmd::PGM_Image(const char*)':
Unidraw/import.cpp:61:34: warning: value computed is not used [-Wunused-value]
--
make[3]: Leaving directory '/builddir/build/BUILD/iv-74f120781bc2def0cc4d1f9f547c07037e8a7a74/src/bin/idraw'
make[3]: Entering directory '/builddir/build/BUILD/iv-74f120781bc2def0cc4d1f9f547c07037e8a7a74/src/bin/idraw'
g++ -DHAVE_CONFIG_H -I. -I. -Div2_6_compatible -I../../include/IV-2_6 -I../../include   -O2 -g -pipe -Wall -Werror=format-security -Wp,-D_FORTIFY_SOURCE=2 -Wp,-D_GLIBCXX_ASSERTIONS -fexceptions -fstack-protector-strong -grecord-gcc-switches -specs=/usr/lib/rpm/redhat/redhat-hardened-cc1 -specs=/usr/lib/rpm/redhat/redhat-annobin-cc1 -m64 -mtune=generic -fasynchronous-unwind-tables -fstack-clash-protection -fcf-protection -c -o ided.o ided.cpp
ided.cpp: In constructor 'IdrawEditor::IdrawEditor(const char*)':
ided.cpp:160:44: warning: dereferencing type-punned pointer will break strict-aliasing rules [-Wstrict-aliasing]
  160 |  if (catalog->Retrieve(file, (Component*&) comp)) {
      |                                            ^~~~
make[3]: Leaving directory '/builddir/build/BUILD/iv-74f120781bc2def0cc4d1f9f547c07037e8a7a74/src/bin/idraw'
make[3]: Entering directory '/builddir/build/BUILD/iv-74f120781bc2def0cc4d1f9f547c07037e8a7a74/src/bin/idraw'

Since these may result in undefined behaviour, they are worth looking into? (I looked at this post to understand the warning better---it has some suggestions on how to handle such issues too).

[sanjayankur31]

build-log.txt