Memleak in IsOptionMember

[Stefan Pöschel]

The ImageMagick version shipped with Ubuntu 16.04 (version 8:6.8.9.9-7ubuntu5.5) is affected by a memory leak. This has been fixed in the following commit:

  http://git.imagemagick.org/repos/ImageMagick/commit/6790815c75bdea0357df5564345847856e995d6b

So I request this fix to be backported to 16.04 (and other affect version, if applicable; 14.04 is not affected).

The tool ODR-PadEnc which I maintain is affected by the bug:

  https://github.com/Opendigitalradio/ODR-PadEnc/issues/2

Here one of the outputs that Valgrind procudes for each invokation - in this case, I used 14.04 with http://archive.ubuntu.com/ubuntu/pool/main/i/imagemagick/imagemagick_6.8.9.9.orig.tar.xz as I have 16.04 only running in a VM. The patches within http://archive.ubuntu.com/ubuntu/pool/main/i/imagemagick/imagemagick_6.8.9.9-7ubuntu5.5.debian.tar.xz do NOT address this bug.

==1961== 455,322 bytes in 111 blocks are definitely lost in loss record 1,761 of 1,762
==1961== at 0x4C2AB80: malloc (in /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so)
==1961== by 0x5E2DB3E: AcquireString (string.c:132)
==1961== by 0x5E2FC10: StringToArgv (string.c:2196)
==1961== by 0x5DC46F7: IsOptionMember (option.c:2278)
==1961== by 0x5F3F789: WritePNGImage (png.c:11996)
==1961== by 0x5D12B11: WriteImage (constitute.c:1184)
==1961== by 0x5CDE340: ImageToBlob (blob.c:1607)
==1961== by 0x40D7A5: SLSManager::encodeFile(std::string const&, int, bool) (sls.cpp:392)
==1961== by 0x4038B1: main (odr-padenc.cpp:324)