Strange behavior of MagickWriteImage

iSage · Post by **iSage** » 2018-02-28T07:31:26-07:00

MagickWriteImage, when working with JPEG, calls open/close on file twice. E.G.:

...
stat("test.jpeg", 0x14e0020)            = -1 ENOENT (No such file or directory)
open("test.jpeg", O_RDWR|O_CREAT|O_TRUNC, 0666) = 3
fstat(3, {st_mode=S_IFREG|0644, st_size=0, ...}) = 0
fstat(3, {st_mode=S_IFREG|0644, st_size=0, ...}) = 0
fstat(3, {st_mode=S_IFREG|0644, st_size=0, ...}) = 0
close(3)                                = 0
stat("test.jpeg", {st_mode=S_IFREG|0644, st_size=0, ...}) = 0
open("test.jpeg", O_RDWR|O_CREAT|O_TRUNC, 0666) = 3
fstat(3, {st_mode=S_IFREG|0644, st_size=0, ...}) = 0
fstat(3, {st_mode=S_IFREG|0644, st_size=0, ...}) = 0
mmap(NULL, 442368, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x7f2d48364000
mmap(NULL, 442368, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x7f2d482f8000
mmap(NULL, 1769472, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x7f2d43319000
write(3, "\377\330\377\340\0\20JFIF\0\1\1\0\0\1\0\1\0\0\377\333\0C\0\3\2\2\3\2\2\3"..., 16384) = 16384
write(3, "\242\201\260\331\4|\36WE\326RIr\23Xr\216\231\351\314\r\16\33\321Ru\345\325)\315;*"..., 4096) = 4096
write(3, "8\272\236GR\267\201\352\251\343d\372\375\17\254\3278r\30\215\337\24n\5\216{\266sW\205\303\307"..., 12288) = 12288
write(3, "z\221n\326\\)mf)\351\313V\237-\346pS\0AR\373\261.}5;i) '\0275"..., 4096) = 4096
write(3, "IZ\315\314\225\ftP\361\35Tr\273.\326\373\276\37\271\257Z\316\263O\240\320\310\347\326\275\233\262"..., 12288) = 12288
write(3, "\255\311\27\233I{\203G2\237\n\351\4\20\340J\26Jv`\270\237u\6\265\263l\246\235J\23\210"..., 4096) = 4096
write(3, "\272\343\22\226\211\254\273q\263\360\250\203\235\203\275\10n\355l\325\323G\271\232\230\2426\224\353hS\331"..., 12288) = 12288
write(3, "\213g?\372\335\257\204]\305\255\314\241\331l\33Q\346!\24\377\0h\355\301\303k\215F\261\370\261\275"..., 4096) = 4096
write(3, "\233\30K\262\177\362T\200\270\321J\304\255XB\3\31\343\304\"\205\322\217\336\33t7\235\342\3#\360"..., 12288) = 12288
write(3, "\0\rb\210\374\324~?\210\277\1`\334)\25ZP\356X\20(}Gk\270\227o$)\3013g"..., 4096) = 4096
write(3, "3\5fV\30\366\304\v\203\22\316\340\22\334\303\210\311\2776\270%\237IA\360\216fK\0\23\271\345"..., 12288) = 12288
write(3, "\263\2238\3013\21\21\310\333\r'\1^\277\327\352d1\10\247\367\6\216\233\276\r?\334\26\320_\10"..., 4096) = 4096
write(3, "\263\324>P\25T\200\177+\314\313#\236\264\177\22\216\316JVE~\241E\202\214\2\5\374\316\v\233"..., 12288) = 12288
write(3, "l\356\30I\257\312\16\322\224\20\225$D\322\364\266\214\302\3652DE\322@c\340\t\304\3d\306Z"..., 4096) = 4096
write(3, "r\237\231h\267m\211r~y&\331w&\313\371\10v\367cf\r\217\33V\204\367\f-c\223o"..., 12288) = 12288
write(3, "\237\370\1\231\353\0\4\214\203\0\241\1Kp\217\301\203AC%V\200\212\f/\0\316\302\22cP\0"..., 4096) = 4096
write(3, "f\303\320@\25\364\0@\302.A\30\300\242\260~\264\4\10\10\2;P\374\206\1\0\240j\250\330I"..., 12288) = 12288
write(3, "\20\16\344\205B\202\222x0Z\3\334\310J.\342\344\213r\24\21\336,\25gs!\242\4 \274\362"..., 4096) = 4096
munmap(0x7f2d43319000, 1769472)         = 0
munmap(0x7f2d482f8000, 442368)          = 0
munmap(0x7f2d48364000, 442368)          = 0
write(3, "\31\363\320D@\213\256\21P0\210\213\316 \2\0\202\f\4.`\20A\0046=\25\243Q\250\334\267"..., 1502) = 1502
fstat(3, {st_mode=S_IFREG|0644, st_size=153054, ...}) = 0
close(3)                                = 0
...

This happens only when writing JPEG files. For PNG and GIF open/close is only called once.
While this doesn't seem like a critical bug, that's definitely strange.