Go version

go version go1.23.1 linux/amd64

Output of go env in your module/workspace:

GO111MODULE=''
GOARCH='amd64'
GOBIN=''
GOCACHE='/home/davecb/.cache/go-build'
GOENV='/home/davecb/.config/go/env'
GOEXE=''
GOEXPERIMENT=''
GOFLAGS=''
GOHOSTARCH='amd64'
GOHOSTOS='linux'
GOINSECURE=''
GOMODCACHE='/home/davecb/go/pkg/mod'
GONOPROXY='*.indexexchange.com'
GONOSUMDB='*.indexexchange.com'
GOOS='linux'
GOPATH='/home/davecb/go'
GOPRIVATE='*.indexexchange.com'
GOPROXY='https://proxy.golang.org,direct'
GOROOT='/usr/local/go1.23'
GOSUMDB='sum.golang.org'
GOTMPDIR=''
GOTOOLCHAIN='auto'
GOTOOLDIR='/usr/local/go1.23/pkg/tool/linux_amd64'
GOVCS=''
GOVERSION='go1.23.1'
GODEBUG=''
GOTELEMETRY='on'
GOTELEMETRYDIR='/home/davecb/.config/go/telemetry'
GCCGO='gccgo'
GOAMD64='v1'
AR='ar'
CC='gcc'
CXX='g++'
CGO_ENABLED='1'
GOMOD='/dev/null'
GOWORK=''
CGO_CFLAGS='-O2 -g'
CGO_CPPFLAGS=''
CGO_CXXFLAGS='-O2 -g'
CGO_FFLAGS='-O2 -g'
CGO_LDFLAGS='-O2 -g'
PKG_CONFIG='pkg-config'
GOGCCFLAGS='-fPIC -m64 -pthread -Wl,--no-gc-sections -fmessage-length=0 -ffile-prefix-map=/tmp/go-build3678357838=/tmp/go-build -gno-record-gcc-switches'

What did you do?

I made a spelling mistake, and tried to link to a CGO function that didn't exist, "C.Cstring".
To my surprise I got ./minimum_code.go:15:13: could not determine kind of name for C.Cstring
That has me looking in all the wrong places!

When, after a nice cup of tea, I spotted the typo, and got a far better error,
/tmp/go-build/minimum_code.cgo2.c:51:(.text+0x8): undefined reference to PDQ_Init

I had been thinking that calling the misspelled function would get me an undefined-reference error, which is more normal.

If this is something that can be fixed, I'd recommend it: Mr Google found lots and lots of discussion of could not determine kind of name for C.Cstring, none relevant. Even a better error message would suffice.

If there really is a Cstring function that you want to keep, bug me about controlling its visibility: Paul Stachour and I have written in the Communications of the ACM about that problem (;-))

package main

// #include <stdio.h>
// #include <math.h>
// #include "../pdq5/lib/PDQ_Lib.h"
import "C"

func main() {
	TestInit()
}

// TestInit is the startup function for the pdq library, tested here
func TestInit() {
	var title string = "closed uniserver"
	C.PDQ_Init(C.Cstring(title)) // title for the report
}

// Results: with C.Cstring, which is spelled wrong, I got
// ./minimum_code.go:15:13: could not determine kind of name for C.Cstring
// with C.CString, I got a good, expected error from ld, which couldn't find PDQ_Init()
// /tmp/go-build/minimum_code.cgo2.c:51:(.text+0x8): undefined reference to `PDQ_Init'
// I'm surprised I didn't get a linkage error for C.Cstring()

What did you see happen?

When misspelled, I got
./minimum_code.go:15:13: could not determine kind of name for C.Cstring

when fixed, I got
/tmp/go-build/minimum_code.cgo2.c:51:(.text+0x8): undefined reference to `PDQ_Init'

I'm surprised I didn't get a linkage error for a missing C.Cstring()

What did you expect to see?

./minimum_code.go:15:13: undefined reference to Cstring