gcc Questions

Ubuntu – GCC Output Symbol not Relocatable with -fPIC

November 14, 2024
TheAhmad
2 Answers

On an Ubuntu 24.04, using the default GCC-13.2 compiler I compiled a source file with -fPIC option to produce relocatable binary: /usr/bin/c++ -v -DBPFTIME_BUILD_WITH_LIBBPF=1 -DSPDLOG_COMPILED_LIB -Dbpftime_text_segment_transformer_EXPORTS -I/home/ahmad/Programs/bpftime/build/build/FridaGum-prefix/src/FridaGum -I/home/ahmad/Programs/bpftime/third_party/spdlog/include -fno-omit-frame-pointer -O3 -DNDEBUG -std=gnu++20 -fPIC -o text_segment_transformer.cpp.o -c /home/ahmad/Programs/bpftime/attach/text_segment_transformer/text_segment_transformer.cpp The compiler output…

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Ubuntu – 31 October skipped, why?

November 4, 2024
Cyriaque
2 Answers

I'm not programming very often; I may have skipped something important but... I expect the following code to write 31st October between 30th October and the 1st November. My output skips the 31st. Is it a bug? Do I misuse…

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How can I find the declaration of sin function in math.h file of GCC in Debian Linux?

November 1, 2024
Abhinav Thakur
2 Answers

I read about C programming language in Yashwant Kanetkar's book Let us C. In Functions chapter I read about sin, cos, tan and pow functions of math.h file. But in this chapter it is written that: You can even open…

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Debian – Truncating floats to int on x86 vs x86_64 has different rounding error

October 27, 2024
umläute
2 Answers

I stumbled upon a failing unit-test, that involves converting doubles to integers. The actual number that is converted is 1.234 * 1000., and the code basically boils down to: #include <iostream> #include <cstdint> int64_t deltatime(double numSeconds) { return (int64_t) (numSeconds…

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Installing gcc13 and g++13 in Debian bookworm rust docker image

October 23, 2024
KaiJun
2 Answers

I am trying to install gcc13 and g++13 in the following Rust docker image. # Builder FROM rust:1-bookworm AS builder RUN apt update RUN apt install software-properties-common -y RUN apt-get install python3-launchpadlib -y RUN add-apt-repository ppa:ubuntu-toolchain-r/test -y RUN apt update…

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Debian – Does GCC optimize out empty method calls?

October 13, 2024
JayDee
2 Answers

The following method functions fine but I am curious as to performance and optimization. Example I call 'Output(str)' to send something to the terminal. I added a method that only outputs if debugging, as follows. Now I am left wondering…

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Ubuntu – Why used printf the same variable addr twice result in different print values?

September 12, 2024
Alan Bai
3 Answers

Environnment: gcc version 9.4.0 (Ubuntu 9.4.0-1ubuntu1~20.04.2)) The conditions under which this occurs are: The printed variable is of float type. There are type conversion errors in the printf. The buffer is refreshed before the printf call. Build command: gcc floatTest.c…

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Centos – Why libgomp keeps creating new thread?

September 10, 2024
Xiaoyong Guo
2 Answers

I'm running a openmp program (gcc and libgomp on CentOS 8.5). I used strace to inspect and found that syscall clone was called over and over again (I posed part of the log below), which I believe implies that openmp…

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Centos – Using the boost::asio::co_spawn function across multiple modules can trigger linker errors

September 10, 2024
Yu Duan
2 Answers

When I use co_spawn across multiple modules and enable optimization levels O2 or O3, I encounter a linker error during the linking phase. It appears that the compiler discards some symbols it deems unused during the linking stage. Minimal reproduce…

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Ubuntu – How to leverage the [*]printf format type specification warnings?

August 27, 2024
Ken P
2 Answers

As we all know and love (or hate), GCC has the capability of issuing warnings when you attempt to use the printf() family of functions with mismatched type specifications. In our code, we have a number of utility functions of…

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