cflow——C语言函数调用关系生成器

前言

拿到一份陌生的 C 工程，想要了解整个工程的脉络，你会使用什么方法呢？

函数调用

一般都是通过函数调用关系来理清整个工程的运作流程，通常使用的软件是 source insight。从 main 函数开始，查看 main 函数调用了哪些函数，然后进入各个子函数。以此类推，逐渐展开整个脉络。我之前也是一直使用这种方法，我称之为“人肉整理”。这种方法是很耗时的，一个不大的工程就可能要整理大半天。从那时起，我就时常想，有没有自动化的软件来干这个事情？后来找到了一款：calltree，听名字就知道它的功能了，“调用树”，用来理清函数调用关系的。不过，该款软件早已停更，版本较老，用起来不太顺手。

cflow

后来又发现了一款：cflow。在 ubuntu 下直接使用命令就可以安装该软件，如下

sudo apt install cflow

cflow 能够分析 C 文件中的控制流，看个例子

$ cflow -T log.c
+-log_init() <void log_init (void) at log.c:193>+-InitializeCriticalSection()+-wget_console_init()+-wget_logger_set_func()+-wget_get_logger()+-write_debug_stderr() <void write_debug_stderr (const char *data, size_t len) at log.c:157>| \-write_debug() <void write_debug (FILE *fp, const char *data, size_t len) at log.c:138>|   \-write_out() <void write_out (FILE *default_fp, const char *data, size_t len, int with_timestamp, const char *colorstring, wget_console_color color_id) at log.c:55>|     +-strcmp()|     +-open()|     +-wget_buffer_init()|     +-isatty()|     +-fileno()|     +-wget_buffer_strcpy()|     +-gettime()|     +-localtime_r()|     +-wget_buffer_printf_append()|     +-wget_buffer_memcat()|     +-wget_buffer_strcat()|     +-fwrite()|     +-EnterCriticalSection()|     +-wget_console_set_fg_color()|     +-fflush()|     +-wget_console_reset_fg_color()|     +-LeaveCriticalSection()|     +-write()|     +-close()|     \-wget_buffer_deinit()
...

tree2dotx

为了更直观地展示函数调用关系，我们可以使用 xdot 工具。不过使用 xdot 工具地前提是我们必须要有一份用 xdot 格式表示节点地文件。这就需要使用另外一个工具 tree2dotx，可以从这里获取，将其存为 tree2dotx 文件，然后放入系统路径。
运行一下看看效果

$ cflow log.c | tree2dotx
digraph G{ranksep = 1;rankdir=LR;size="1920,1080";node [fontsize=16,fontcolor=blue,style=filled,fillcolor=Wheat,shape=box];"log_init" -> "InitializeCriticalSection";"log_init" -> "wget_console_init";"log_init" -> "wget_logger_set_func";"log_init" -> "wget_get_logger";"log_init" -> "write_debug_stderr";"write_debug_stderr" -> "write_debug";"write_debug" -> "write_out";"write_out" -> "strcmp";"write_out" -> "open";"write_out" -> "wget_buffer_init";"write_out" -> "isatty";"write_out" -> "fileno";"write_out" -> "wget_buffer_strcpy";"write_out" -> "gettime";"write_out" -> "localtime_r";
...
}

xdot

xdot 功能能够以图形的方式展示节点之间的关系，在 ubuntu 下使用 apt 命令就可以安装

sudo apt install xdot

运行看下效果

$ cflow log.c | tree2dotx > out.dot
$ xdot out.dot

可以非常直观的看到 log.c 文件中的函数调用关系，鼠标放在某个函数上，前后的箭头还会变成红色，用来指示被调用和调用关系。

优化

上述 tree2dotx 脚本其实是有点问题的，我对它做了一些优化，如下

去重。经过 tree2dotx 处理过的节点，有重复的，导致连线翻倍，去重后效果如下，和上面对比是不是简洁多了

命令如下

cflow log.c | tree2dotx | awk '!a[$0]++' > out.dot

去除多余空格
原始 tree2dotx 脚本在将函数调用关系转成节点时，有些函数后面多出了一个空格，将脚本中的 sed -e "s/<.*>.*//g" | tr -d '\(' | tr -d '\)' | tr '|' ' ' 改成 sed -e "s/ <.*>.*//g" | tr -d '\(' | tr -d '\)' | tr '|' ' '，就可以了。
增加子节点
这样就可以显示当前函数属于哪个 C 文件了

附件

优化后的 tree2dotx 完整代码

$ cat /usr/local/bin/tree2dotx
#!/bin/bash
#
# tree2dotx --- transfer a "tree"(such as the result of tree,calltree,cflow -b)
#                 to a picture discribed by DOT language(provided by Graphviz)
#
# Author: falcon <wuzhangjin@gmail.com>
# Update: 2007-11-14, 2015-3-19
# Usage:
#
#       tree -L 2 -d /path/to/a/directory | bash tree2dotx | dot -Tsvg -o tree.svg
#       cd /path/to/a/c/project/; calltree -gb -np -m *.c | bash tree2dotx | dot -Tsvg -o calltree.svg
#       cd /path/to/a/c/project/; cflow -b -m setup_rw_floppy kernel/blk_drv/floppy.c | bash tree2dotx | dot -Tsvg -o cflow.svg
## Set the picture size, direction(LR=Left2Right,TB=Top2Bottom) and shape(diamond, circle, box)
size="1920,1080"
direction="LR"
shape="box"# color, X11 color name: http://en.wikipedia.org/wiki/X11_color_names
fontcolor="blue"
fillcolor="Wheat"# fontsize
fontsize=16# Specify the symbols you not concern with space as decollator here
filterstr="";input=`cat`# output: dot, flame
output="dot"has_subgraph="0"
ordering="0"# Usage#grep -v ^$ | catfunction usage
{echo ""echo "  $0 "echo ""echo "     [ -f  \"filter1 filter2 ...\" ]"echo "     [ -s  size, ex: 1080,760; 1920,1080 ]"echo "     [ -d  direction, ex: LR; TB ]"echo "     -h  get help"echo ""
}function subgraph() {echo "$input" \| grep -e " at " \| sed 's/).* at /)/g;s/:.*//g;s/ //g' \| sed -r 's/^(.*)\(\)(.*)$/\tsubgraph "cluster_\2" { label="\2";\1;}/' \| sort -u
}while getopts "f:s:S:d:e:h:o:r:" opt;
docase $opt inf)filterstr=$OPTARG;;s)size=$OPTARG;;S)shape=$OPTARG;;d)direction=$OPTARG;;e)has_subgraph=$OPTARG;;o)output=$OPTARG;;r)ordering=$OPTARG;;h|?)usage $0;exit 1;;;esac
done# Transfer the tree result to a file described in DOT languageecho "$input" | \
grep -v ^$ | grep -v "^[0-9]* director" \
| sed -e "s/ <.*>.*//g" | tr -d '\(' | tr -d '\)' | tr '|' ' ' \
| sed -e "s/ \[.*\].*//g" \
| awk '{if(NR==1) system("basename "$0); else printf("%s\n", $0);}' \
| awk -v fstr="$filterstr" '# function for filter the symbols you not concernfunction need_filter(node) {for ( i in farr ) {if (match(node,farr[i]" ") == 1 || match(node,"^"farr[i]"$") == 1) {return 1;}}return 0;}BEGIN{# Filternode array are used to record the symbols who have been filtered.oldnodedepth = -1; oldnode = ""; nodep[-1] = ""; filter[nodep[-1]] = 0;oldnodedepth_orig = -1; nodepre = 0; nodebase = 0; nodefirst = 0;output = "'$output'";#printf("output = %s\n", output);# Store the symbols to an array farrsplit(fstr,farr," ");# print some setting infoif (output == "dot") {printf("digraph G{\n");if(ordering == "1") {printf("ordering=out;\n");}printf("ranksep = 1;\n");printf("\trankdir='$direction';\n");printf("\tsize=\"'$size'\";\n");printf("\tnode [fontsize='$fontsize',fontcolor='$fontcolor',style=filled,fillcolor='$fillcolor',shape='$shape'];\n");}}{# Get the node, and its depth(nodedepth)# nodedepth = match($0, "[^| `]");nodedepth = match($0, "[[:digit:]|[:alpha:]]|[[:alnum:]]");node = substr($0,nodedepth);# printf("%d %d %s \n", nodedepth, oldnodedepth_orig, node);if (nodefirst == 1 && oldnodedepth_orig > 0) {nodefirst = 0;nodebase = nodedepth-oldnodedepth_orig;}if (nodedepth == 0)nodedepth=1;tmp = nodedepth;# printf("pre=%d base=%d np=%d oldnp=%d node=%s \n", nodepre, nodebase, tmp, oldnodedepth_orig, node);if (nodedepth != 0 && oldnodedepth_orig == -1) {nodepre = nodedepth-1;nodefirst = 1;nodedepth = 0;} else if (nodebase != 0) {nodedepth = int((nodedepth-nodepre)/nodebase);}# if whose depth is 1 less than him, who is his parentif (nodedepth-oldnodedepth == 1) {nodep[nodedepth-1] = oldnode;}# for debugging# printf("%d %s\n", nodedepth, node);# printf("\t\"%s\";\n",node);# print the vectorsif (oldnodedepth != -1) {# if need filter or whose parent have been filter, not print it, and set the flat of filter to 1if (need_filter(node) || filter[nodep[nodedepth-1]] == 1) {filter[node] = 1;#       printf("node = %s, filter[node] = %d\n", node, filter[node]);} else if (nodep[nodedepth-1] != "") {if (output == "dot") {printf("\t\"%s\" -> \"%s\";\n", nodep[nodedepth-1], node, nodep[nodedepth-1], node);} else {for (i = 0; i < nodedepth; i++)printf("%s;", nodep[i]);printf("%s 1\n", node);}#       printf("\t\"%s\" -> \"%s\"[label=\"%s>%s\"];\n", nodep[nodedepth-1], node, nodep[nodedepth-1], node);}}# save the old depth and the old nodeoldnodedepth_orig = tmp;oldnodedepth = nodedepth;oldnode = node;} END {#                if (output == "dot")
#           printf("}");}'echo ""
if [ $has_subgraph == "1" ]
thensubgraph
fi
echo "}"

cflow -d 3 wget.c | tree2dotx -e 1 -r 1 | awk '!a[$0]++' > out.dot && cat out.dot

tree2dotx -e 0/1 指定是否展示子图（函数所在文件）
tree2dotx -r 0/1 指定是否按照函数出现顺序展示图像

图像

还可以将 xdot 显示的图像输出为图片

dot -Tgif out.dot -o out.gif

参考

https://graphviz.gitlab.io/_pages/pdf/dotguide.pdf