CODEWITHSUNDEEP
gccglibclibc
badnack
badnack

Reputation: 767

GLibc optimizations required

Why is it not possible recompile GLibc turning off all the optimizations (i.e., -O0)?

Particularly in doing this:

make CFLAGS='-O0 -w' CXXFLAGS='-O0 -w'

I get:

 #error "glibc cannot be compiled without optimization"

Upvotes: 7

Views: 3175

Answers (3)

user21695297
user21695297

Reputation: 1

By Slackware operating system version 15. In the folder:

/home/wsys0/glibc/glibc-2.36/build/

Create a file name cmp:

chmod 700 cmp

Put the following line into cmp:

export CFLAGS="-Wno-error -O3 -g"
../configure --prefix=/home/wsys0/glibc/out --disable-sanity-checks

Then run: ./cmp, to install it.

Reference: https://sky-bro.github.io/posts/compile-and-use-your-own-glibc/

Upvotes: 0

user541686
user541686

Reputation: 210445

When I Google the error, the first result tells me exactly why.

"In the early startup of the dynamic loader (_dl_start), before relocation of the PLT, you cannot make function calls. You must inline the functions you will use during early startup, or call compiler builtins (__builtin_*).

Without optimizations enabled GCC will not inline functions. The early startup of the dynamic loader will make function calls via an unrelocated PLT and crash." -- Carlos O'Donell

Upvotes: 8

Mike Robinson
Mike Robinson

Reputation: 8945

Basically: "glibc is voodoo!" This one "library of all libraries" has a very special place in any system, because virtually(?) everything else in the entire system relies upon it.

Therefore, if "someone out there" took the time to prevent you from compiling this library "without optimizations," I cordially invite you to take him/her at their word. "There must be a [very good] reason."

Upvotes: 3

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