buildmode=pie wrongly strips the .gopclntab symbol

[kp-liviu-peles]

Go version

go version go1.22.2 linux/arm64

Output of go env in your module/workspace:

GO111MODULE=''
GOARCH='arm64'
GOBIN=''
GOCACHE='/home/dev/.cache/go-build'
GOENV='/home/dev/.config/go/env'
GOEXE=''
GOEXPERIMENT=''
GOFLAGS=''
GOHOSTARCH='arm64'
GOHOSTOS='linux'
GOINSECURE=''
GOMODCACHE='/home/dev/go/pkg/mod'
GONOPROXY=''
GONOSUMDB=''
GOOS='linux'
GOPATH='/home/dev/go'
GOPRIVATE=''
GOPROXY='https://proxy.golang.org,direct'
GOROOT='/usr/lib/go-1.22'
GOSUMDB='sum.golang.org'
GOTMPDIR=''
GOTOOLCHAIN='auto'
GOTOOLDIR='/usr/lib/go-1.22/pkg/tool/linux_arm64'
GOVCS=''
GOVERSION='go1.22.2'
GCCGO='gccgo'
AR='ar'
CC='gcc'
CXX='g++'
CGO_ENABLED='1'
GOMOD='/home/dev/repos_shared/<repo_name>/go.mod'
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 -pthread -Wl,--no-gc-sections -fmessage-length=0 -ffile-prefix-map=/tmp/go-build272344516=/tmp/go-build -gno-record-gcc-switches'

What did you do?

I am cross-compiling my project for linux/riscv64. Including -buildmode=pie wrongly strips the .gopclntab symbol.
I checked this with readelf -S <exe_name> | grep gopclntab.
Removing -buildmode=pie gives the correct symbol table.

Below is the command that gave me the correct symbol table. I had to replace a couple of paths and stuff since the repo is private.
CGO_ENABLED=1 CGO_CFLAGS="-I<lib/include> -I -Wno-incompatible-pointer-types -fstack-protector-strong -D_FORTIFY_SOURCE=2" CGO_LDFLAGS="-L<lib/include> -l<lib_binary> -Wl,-z,now,-z,relro" GOROOT_FINAL=/ \ "/usr/bin/go" build -mod=vendor -gcflags="all=-N -l -trimpath={PROJECT_DIR}" -asmflags="all=-trimpath={PROJECT_DIR}" -tags Debug -ldflags " -X main.Version=1-X main.Build=aaa -X main.Branch= -X main.ClientVersion=1 -X main.ClientBuild=aaa -extldflags '-L <lib/include> -Wl,-z,now,-z,relro'" -o bin/ ./path/to/code

What did you see happen?

.gopclntab symbol was not included in the -buildmode=pie case.

What did you expect to see?

gopclntab should be included in the symbol table when the '-buildmode=pie' flag is included in the build command.

[ianlancetaylor]

A point about terminology: readelf -S prints sections, not symbols.

More importantly, readelf -S is, unfortunately, broken by default. It truncates section names. You must always use readelf -S --wide. If you do that, your grep operation will discover the .data.rel.ro.gopclntab section.

Either way, you can more easily find the section using symbols, not sections. That works the same for PIE or not. Use readelf -s --wide and look for the runtime.pclntab (start of pclntab) and runtime.epclntab (end of pclntab) symbols.

[kp-liviu-peles]

A point about terminology: readelf -S prints sections, not symbols.

More importantly, readelf -S is, unfortunately, broken by default. It truncates section names. You must always use readelf -S --wide. If you do that, your grep operation will discover the .data.rel.ro.gopclntab section.

Either way, you can more easily find the section using symbols, not sections. That works the same for PIE or not. Use readelf -s --wide and look for the runtime.pclntab (start of pclntab) and runtime.epclntab (end of pclntab) symbols.

Thanks for the reply !

Apologies for the misused terminology.

I forgot to mention that dlv would also fail with missing dwarf symbols when .gopclntab is omitted. ( And i checked all the debug symbols would be there ). Although this is likely a dlv issue.