How to compile libstdc++ with specific compiler option?

Question

I want to compile libstdc++ with the -fno-omit-frame-pointer option for profiling purposes, if possible. I was able to build libstdc++ by following https://gcc.gnu.org/install/index.html, but how can I set the option? The CXXFLAGS approach did not work.

Answer 1

Hints https://www.linuxfromscratch.org/lfs/view/stable/chapter06/gcc-pass2.html

A test-build ....

tar xvf gcc-10.3.0.tar.xz
mkdir BUILD__libstdc++103
cd BUILD__libstdc++103/

../gcc-10.3.0/libstdc++-v3/configure \
    CXXFLAGS="-g -O2 -D_GNU_SOURCE -fno-omit-frame-pointer" \
    --prefix=/home/knudfl/BUILD__libstdc++103/usr \
    --disable-multilib --disable-libstdcxx-pch 

make
make install

Seems to be OK : The text -fno-omit-frame-pointer is visible in the terminal make output.

Answer 2

Minimal step-by-step example

Compile GCC from source. Condensed commands:

sudo apt-get build-dep gcc
git clone git://gcc.gnu.org/git/gcc.git
cd gcc
git checkout gcc-6_4_0-release
./contrib/download_prerequisites
mkdir build
cd build
../configure --enable-languages=c,c++ --prefix="$(pwd)/install"
make -j`nproc`

Wait from 30-minutes to two hours. Now let's use this test program a.cpp:

#include <cassert>
#include <queue>

int main() {
    std::priority_queue<int> q;
    q.emplace(2);
    q.emplace(1);
    q.emplace(3);
    assert(q.top() == 3);
    q.pop();
    assert(q.top() == 2);
    q.pop();
    assert(q.top() == 1);
    q.pop();
}

First compile and run it to ensure that the initial compilation worked:

gcc/build/install/bin/g++ -g -std=c++11 -O0 -o a.out ./a.cpp
./a.out

Now let's hack up the priority_queue constructor.

First, you can find the actual constructor easily with GDB as explained at: https://stackoverflow.com/questions/11266360/when-should-i-use-make-heap-vs-priority-queue/51945521#51945521

So we hack it up with this patch:

diff --git a/libstdc++-v3/include/bits/stl_queue.h b/libstdc++-v3/include/bits/stl_queue.h
index 5d255e7300b..deec7bc4d99 100644
--- a/libstdc++-v3/include/bits/stl_queue.h
+++ b/libstdc++-v3/include/bits/stl_queue.h
@@ -61,6 +61,7 @@
 #if __cplusplus >= 201103L
 # include <bits/uses_allocator.h>
 #endif
+#include <iostream>
 
 namespace std _GLIBCXX_VISIBILITY(default)
 {
@@ -444,7 +445,10 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
       priority_queue(const _Compare& __x = _Compare(),
             _Sequence&& __s = _Sequence())
       : c(std::move(__s)), comp(__x)
-      { std::make_heap(c.begin(), c.end(), comp); }
+      {
+        std::cout << "hacked" << std::endl;
+        std::make_heap(c.begin(), c.end(), comp);
+      }
 
       template<typename _Alloc, typename _Requires = _Uses<_Alloc>>
    explicit

Then rebuild and re-install just libstdc++ to save a lot of time:

cd gcc/build/x86_64-pc-linux-gnu/libstdc++-v3
make -j`nproc`
make install

and now the next build and run:

gcc/build/install/bin/g++ -g -std=c++11 -O0 -o a.out ./a.cpp
./a.out

outputs:

hacked

Tested on Ubuntu 16.04.

glibc

As a bonus, if you are also interested in C: https://stackoverflow.com/questions/847179/multiple-glibc-libraries-on-a-single-host/52454603#52454603

Related:

• https://stackoverflow.com/questions/21872229/how-to-edit-and-re-build-the-gcc-libstdc-c-standard-library-source/51946224#51946224