Hi,
it looks like my initial reply wasn't entirely correct. It should build
if you pass in both the `.go` file and the `.c` file.
On 18.03.20 15:02, Nitish Saboo wrote:
Hi Gregor,
nitish
main.go
node.c
node.h
I compiled using 'go build -v -x main.go'
But if my cgo directive is defined in main.go, this should have
compiled successfully..right? But it fails with the following whereas
'go build -v -x' works fine.
/tmp/go-build439591561/b001/_x002.o: In function
`_cgo_5637ad3d75e4_Cfunc_load_pattern_db':
/tmp/go-build/cgo-gcc-prolog:86: undefined reference to `load_pattern_db'
collect2: error: ld returned 1 exit status
package main
//#include <stdlib.h>
//#include "node.h"
import "C"
import (
"fmt"
_ "fmt"
"os"
"path"
"unsafe"
)
Please let me know what am I missing here?
Thanks,
Nitish
On Wed, Mar 18, 2020 at 7:20 PM Nitish Saboo <nitish.sabo...@gmail.com
<mailto:nitish.sabo...@gmail.com>> wrote:
Hi Gregor,
Got your point.Thank you for your response.
That explains why the binaries have different names post compilation.
Thanks,
Nitish
On Wed, Mar 18, 2020 at 7:06 PM Gregor Best <b...@pferdewetten.de
<mailto:b...@pferdewetten.de>> wrote:
Hi,
In both `go build main.go`-examples, you tell the compiler to
_only_ build `main.go`.
In your first example, `main.go` probably imports both `util`
and `lib` (you might want to give them less generic names by
the way). The go compiler thus knows "to build `main.go`, I
need to build both `util` and `lib` and link them in".
In the second example, it has no way of knowing where
`load_pattern_db` comes from, since you didn't tell it to
compile a file that defines that function.
The examples where you omit the `main.go` tell the compiler
"build the package in this directory", which includes all
`.go`-files in the directory. `node.c` and `node.h` are likely
built because of `cgo` directives in `a.go`.
The compiler and linker did exactly as you told them to.
On 18.03.20 14:17, Nitish Saboo wrote:
Hi,
*Case 1
----------
*
I have a project called 'nitish' where the folder structure
looks like the following:
nitish
main.go
util
util.go
lib
node.c
node.h
a.go
When I try compiling this project in the following ways:
1) go build -v - x
>> This creates a binary called 'nitish'
2) go build -v - x main.go
>> This creates a binary called 'main'
ldd output of both the binaries is the same.
*Case 2
----------*
Now, when I restructure the project 'nitish' in the following
manner:
nitish
main.go
util.go
node.c
node.h
a.go
When I try compiling this project in the following ways:
1) go build -v - x
>> This creates a binary called 'nitish'
2) go build -v - x main.go
>> This error out with the following:
/tmp/go-build074530518/b001/_x002.o: In function
`_cgo_8eab385aa676_Cfunc_load_pattern_db':
/tmp/go-build/cgo-gcc-prolog:86: undefined reference to
`load_pattern_db'
collect2: error: ld returned 1 exit status
1) In Case 1, why the binaries are created with different
names though both the binaries have the same 'ldd output' and
work the same manner?
2) Why we see an error with the command 'go build -v - x
main.go' in Case 2 but not in Case 1?
Thanks,
Nitish
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