Red Hat ENTERPRISE LINUX 3 - DEVELOPER TOOLS GUIDE Bedienungsanleitung PDF herunterladen (Seite 20)

16 Chapter 3. Developing with Red Hat Enterprise Linux Developer Tools

#1 0x15c in main () at hello.c:18

13. To exit the program and quit the debugger, type:

quit

3.5. Assembler Listings

The compiler normally turns a text based source ﬁle into a binary object ﬁle. It is possible however

to instruct it to just convert the source code into assembler and stop there. The -S option does this.

It also possible to instruct the compiler to produce an assembler listing as well as an object ﬁle. That

can be done as follows:

gcc -c -O2 -Wa,-al hello.c

-c tells GCC to compile or assemble source ﬁles, but not to link them. -O2 produces more fully

optimized code. These are both optional. -Wa tells the compiler to pass the comma-separated list of

options which follows it on to the assembler. The -al option is an assembler option to request an

assembler listing.

This example shows a partial excerpt of an assembler listing for an x386-based target.

29 .text

30 0027 90 .p2align 2„3

31 .globl main

32 .type main,@function

33 main:

34 0028 55 pushl %ebp

35 0029 89E5 movl %esp, %ebp

36 002b 83EC08 subl $8, %esp

37 002e 83E4F0 andl $-16, %esp

38 0031 83EC0C subl $12, %esp

39 0034 680E0000 pushl $.LC1

39 00

40 0039 C7050000 movl $3, a

40 00000300

40 0000

41 0043 E8FCFFFF call puts

41 FF

42 0048 C7042404 movl $4, (%esp)

Example 3-2. Assembly listing excerpt

It also possible to produce an assembler listing that intermixes the original input source code with

the assembler instructions produced by the compiler. This can help track down bugs, discover how

the compiler handles certain language constructs (such as function calls) and to learn more about

assembly language. To do this, just add an h to the assembler option like this:

gcc -c -g -O2 -Wa,-alh hello.c

3.6. Disassembling

The objdump tool can be used to to produce an disassembly of an object or executable ﬁle. It is used

like this:

objdump -d hello.o

1 2 ... 15 16 17 18 19 20 21 22 23 24

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