what does the weak_alias function do and where is it defined
Solution 1
from https://github.com/lattera/glibc/blob/master/include/libc-symbols.h
/* Define ALIASNAME as a weak alias for NAME.
If weak aliases are not available, this defines a strong alias. */
# define weak_alias(name, aliasname) _weak_alias (name, aliasname)
# define _weak_alias(name, aliasname) \
extern __typeof (name) aliasname __attribute__ ((weak, alias (#name)));
About weak symbol:
https://en.wikipedia.org/wiki/Weak_symbol
Solution 2
It is a macro that does the following:
It declares a weak function, if you didnt provide a strong symbol name for that function it will call the function you have laised it to. for example
int _foo(){ return 1;}
//And weak alias
int __attribute__((weak, alias("_foo"))) foo();
So if you haven't provided actual implementation for foo it will basically use _foo and return 1.
Programmer123
Updated on June 22, 2022Comments
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Programmer123 about 2 years
So I'm looking through the source of gcc compiler and I've come along this in fork.c:
int __fork () { __set_errno (ENOSYS); return -1; } libc_hidden_def (__fork) stub_warning (fork) weak_alias (__fork, fork) #include <stub-tag.h>
I'm trying to figure out what weak_alias does. I've used the grep command inside the glibc source files to find all occurrences of #define weak_alias:
grep -r "#define weak_alias"
I've found many occurrences of the macro:
#define weak_alias(n, a)
but the macros don't actually explain anything. They just define that statement they don't show how its being replaced. For example one occurrence is in profil.c:
/* Turn off the attempt to generate ld aliasing records. */ #undef weak_alias #define weak_alias(a,b)
So any ideas what weak_alias does and where it is being defined?
Thanks in advance