free(): invalid next size (fast)

C語言編程成老是 報錯誤：free(): invalid next size (fast)。仔細  原來錯在 malloc語句，將原來的

line=(char *)malloc(sizeof(num))    改成   line=(char *)malloc(num) // 由於num自己爲一個整數，本來就是須要分派長度爲num的內存，開始錯寫成  sizeof（num）；

--------------------------------------------------------------------------
*** Error in `./a.out': free(): invalid next size (fast): 0x0000000000927520 ***
======= Backtrace: =========
/lib64/libc.so.6(+0x7d053)[0x7fc945a59053]
./a.out[0x405aad]
./a.out[0x4028b4]
./a.out[0x402cc4]
./a.out[0x4029fb]
./a.out[0x402ce1]
./a.out[0x40289d]
./a.out[0x402cc4]
./a.out[0x402df2]
./a.out[0x402f96]
./a.out[0x401163]
/lib64/libc.so.6(__libc_start_main+0xf5)[0x7fc9459fdb15]
./a.out[0x400ed9]
======= Memory map: ========
00400000-0040a000 r-xp 00000000 ca:01 2098068                            /data/script/C_script/a.out
00609000-0060a000 r--p 00009000 ca:01 2098068                            /data/script/C_script/a.out
0060a000-0060b000 rw-p 0000a000 ca:01 2098068                            /data/script/C_script/a.out
00927000-00948000 rw-p 00000000 00:00 0                                  [heap]
7fc940000000-7fc940021000 rw-p 00000000 00:00 0 
7fc940021000-7fc944000000 ---p 00000000 00:00 0 
7fc9457c6000-7fc9457db000 r-xp 00000000 ca:01 132855                     /usr/lib64/libgcc_s-4.8.5-20150702.so.1
7fc9457db000-7fc9459da000 ---p 00015000 ca:01 132855                     /usr/lib64/libgcc_s-4.8.5-20150702.so.1
7fc9459da000-7fc9459db000 r--p 00014000 ca:01 132855                     /usr/lib64/libgcc_s-4.8.5-20150702.so.1
7fc9459db000-7fc9459dc000 rw-p 00015000 ca:01 132855                     /usr/lib64/libgcc_s-4.8.5-20150702.so.1
7fc9459dc000-7fc945b93000 r-xp 00000000 ca:01 132825                     /usr/lib64/libc-2.17.so
7fc945b93000-7fc945d93000 ---p 001b7000 ca:01 132825                     /usr/lib64/libc-2.17.so
7fc945d93000-7fc945d97000 r--p 001b7000 ca:01 132825                     /usr/lib64/libc-2.17.so
7fc945d97000-7fc945d99000 rw-p 001bb000 ca:01 132825                     /usr/lib64/libc-2.17.so
7fc945d99000-7fc945d9e000 rw-p 00000000 00:00 0 
7fc945d9e000-7fc945dbf000 r-xp 00000000 ca:01 151333                     /usr/lib64/ld-2.17.so
7fc945fb1000-7fc945fb4000 rw-p 00000000 00:00 0 
7fc945fbb000-7fc945fbf000 rw-p 00000000 00:00 0 
7fc945fbf000-7fc945fc0000 r--p 00021000 ca:01 151333                     /usr/lib64/ld-2.17.so
7fc945fc0000-7fc945fc1000 rw-p 00022000 ca:01 151333                     /usr/lib64/ld-2.17.so
7fc945fc1000-7fc945fc2000 rw-p 00000000 00:00 0 
7fff3ed0c000-7fff3ed2d000 rw-p 00000000 00:00 0                          [stack]
7fff3ed8e000-7fff3ed90000 r-xp 00000000 00:00 0                          [vdso]
ffffffffff600000-ffffffffff601000 r-xp 00000000 00:00 0                  [vsyscall]
Aborted