The program can't start because cygwin1.dll is missing... in Eclipse CDT
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I've had Eclipse for Java on my computer for a few years, and decided to install the CDT and learn C. I installed both MinGW and Cygwin and the CDT detects and tries to use them when I make a new project.

I choose File > New C++ Project and choose Hello World C++ Project and the CygwinGCC toolchain. I name the project "asdf" and hit "Build Debug" in the toolbar. The compiler completes without error. I hit Run and nothing happens.

Browsing to the project directory manually and running asdf.exe gives me an error saying:
"The program can't start because cygwin1.dll is missing from your computer. Try reinstalling the program to fix this problem."

The same thing happens using MinGW, only a different dll is missing.
What do I need to do to have a usable .exe?
(I'm running Windows 7 x64 and the newest version of Eclipse and the CDT.)

EDIT: The compiler output is as follows:

**** Build of configuration Debug for project asdf ****

make all 
Building file: ../src/asdf.cpp
Invoking: Cygwin C++ Compiler
g++ -O0 -g3 -Wall -c -fmessage-length=0 -MMD -MP -MF"src/asdf.d" -MT"src/asdf.d" -o"src/asdf.o" "../src/asdf.cpp"
cygwin warning:
  MS-DOS style path detected: C:\Users\Shawn\Dropbox\eclipse\asdf\Debug
  Preferred POSIX equivalent is: /cygdrive/c/Users/Shawn/Dropbox/eclipse/asdf/Debug
  CYGWIN environment variable option "nodosfilewarning" turns off this warning.
  Consult the user's guide for more details about POSIX paths:
    http://cygwin.com/cygwin-ug-net/using.html#using-pathnames
Finished building: ../src/asdf.cpp

Building target: asdf.exe
Invoking: Cygwin C++ Linker
g++  -o"asdf.exe"  ./src/asdf.o   
Finished building target: asdf.exe
November answered 19/7, 2011 at 18:59 Comment(0)
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This error message means that Windows isn't able to find "cygwin1.dll". The Programs that the Cygwin gcc create depend on this DLL. The file is part of cygwin , so most likely it's located in C:\cygwin\bin. To fix the problem all you have to do is add C:\cygwin\bin (or the location where cygwin1.dll can be found) to your system path. Alternatively you can copy cygwin1.dll into your Windows directory.

There is a nice tool called DependencyWalker that you can download from http://www.dependencywalker.com . You can use it to check dependencies of executables, so if you inspect your generated program it tells you which dependencies are missing and which are resolved.

Drachm answered 19/7, 2011 at 19:13 Comment(12)
It worked! It needed a couple more dlls, too. So I'm assuming the only way to make standalone .exes is to use VisualStudio, then?November
What I should add is that you can copy the DLLs into the same directory as the exe. The exes built by VisualStudio usualy have dependencies too, e.g. to MSVCR71.DLLDrachm
Hello. In my case, mutliple .dll are missing because my folder is called C:\cygwin64\bin. Do you think it's safe to just erase the 64 or is there a smarter way around this? ThanksBullfrog
@Marco: Why don't you just add C:\cygwin64\bin to your system path? I guess your binary is compiled as 64bit.Drachm
@Drachm I tried to add it to my PATH (system and user variable PATH) and it didn't work. I also copied it to `C:` with no favorable result.Lattice
@Jossie Have you tried analyzing your problem with DependencyWalker?Drachm
@Drachm In DependencyWalker, CYGWIN1.DLL is shown as red. What can I do now?Lattice
@Drachm I typoed, forgot to add a ; before the last folder, and also typed C:cygwin64\bin. The problem is now resolved.Lattice
If a program needs cygwin1.dll, does that mean it also requires a cygwin installation? Or can it run on any machine so long as the dll is present?Horde
For me it worked when adding cygwin1.dll to C:\windows directory.Rm
@ShawnWalton " So I'm assuming the only way to make standalone .exes is to use VisualStudio, then?" -- Why the heck would you assume that? You don't even need VS to run Microsoft's C compiler, let alone all the other compilers that run on Windows.Bulky
For me, what actually worked was adding the whole of Cygwin bin to my path for Windows 8, legacy support is a female dog...Giraldo
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You can compile with either Cygwin's g++ or MinGW (via stand-alone or using Cygwin package). However, in order to run it, you need to add the Cygwin1.dll (and others) PATH to the system Windows PATH, before any cygwin style paths.

Thus add: ;C:\cygwin64\bin to the end of your Windows system PATH variable.

Also, to compile for use in CMD or PowerShell, you may need to use:

x86_64-w64-mingw32-g++.exe -static -std=c++11 prog_name.cc -o prog_name.exe

(This invokes the cross-compiler, if installed.)

Tidemark answered 3/12, 2018 at 18:42 Comment(2)
Thank you so much for your help @not2qubit. But you forgot to put a colon in the ';C\cygwin64\bin' string, right after 'C'. I think it would be better to edit your answer. Because I was a bit confused at first. Bests ...Orderly
Hi @Orderly I've now fixed. ThanksTidemark
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To add to this and save someone another google, just do this in cmd:

set PATH=%PATH%;C:\cygwin64\bin
Monck answered 10/11, 2021 at 18:15 Comment(0)

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