7.6

	in .symtab?	type	module	section
buf	Yes	external	m	.data
bufp0	Yes	global	swap	.data
bufp1	Yes	local	swap	.bss
swap	Yes	global	swap	.text
temp	No	------	-----	------
incr	Yes	local	swap	.text
count	Yes	local	swap	.bss

7.7

删除行 x = -0.0;
或者
int x 改成 double x

7.8

A.
main.1
main.2

B.
unknown
unknown

C.
error
error

7.9

0xe5894855 is 函数main的前2个指令内容。

7.10

A.
gcc p.o libx.a

B.
gcc p.o libx.a liby.a libx.a

C.
gcc p.o libx.a liby.a libx.a libz.a

7.11

.bss 的空间

7.12

A.
ADDR(s) = ADDR(.text) = 0x4004e0
ADDR(r.symbol) = ADDR(swap) = 0x4004f8
refaddr = ADDR(s) + r.offset = 0x4004ea
*refptr = (unsigned) (ADDR(r.symbol) + r.addend - refaddr) = 0xa

B.
ADDR(s) = ADDR(.text) = 0x4004d0
ADDR(r.symbol) = ADDR(swap) = 0x400500
refaddr = ADDR(s) + r.offset = 0x4004da
*refptr = (unsigned) (ADDR(r.symbol) + r.addend - refaddr) = 0x22

7.13

7.13

A.

libm.a path

whereis libm.a

output:

libm: /usr/lib64/libm.a /usr/lib64/libm.so

libm.a files

ar t /usr/lib64/libm.a

output:

s_lib_version.o
s_matherr.o
s_signgam.o
fclrexcpt.o
fgetexcptflg.o
fraiseexcpt.o
fsetexcptflg.o
ftestexcept.o
fegetround.o
fesetround.o
fegetenv.o
feholdexcpt.o
fesetenv.o
feupdateenv.o
t_exp.o
fedisblxcpt.o
feenablxcpt.o
fegetexcept.o
powl_helper.o
e_acos.o
e_acosh.o
e_asin.o
e_atan2.o
e_atanh.o
....

similar way for libc.a

B.

compile code with -Og and -Og -g

不一样

C.

ldd /usr/bin/gcc

    linux-vdso.so.1 =>  (0x00007ffe99d2f000)
    libm.so.6 => /lib64/libm.so.6 (0x00007fc91fb6a000)
    libc.so.6 => /lib64/libc.so.6 (0x00007fc91f7a7000)
    /lib64/ld-linux-x86-64.so.2 (0x00005646f33c1000)