gcc -frecord-gcc-switches为此提供了一个选项：
-frecord-gcc-switches
This switch causes the command line that was used to invoke the compiler to
be recorded into the object file that is being created. This switch is only
implemented on some targets and the exact format of the recording is target
and binary file format dependent, but it usually takes the form of a section
containing ASCII text.
之后，ELF可执行文件将包含.GCC.command.line带有该信息的部分。
$ gcc -O2 -frecord-gcc-switches a.c
$ readelf -p .GCC.command.line a.out
String dump of section '.GCC.command.line':
[ 0] a.c
[ 4] -mtune=generic
[ 13] -march=x86-64
[ 21] -O2
[ 25] -frecord-gcc-switches
当然，如果没有该选项编译的可执行文件将无法使用。
对于简单的优化情况，如果文件是使用调试信息编译的，则 可以 尝试使用调试器。如果稍稍进行，可能会注意到一些变量已被“优化”。这表明发生了优化。
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