4 Commits

Author	SHA1	Message	Date
Russ Cox	a987aaf5f7	cmd/compile: require -p flag ... The -p flag specifies the import path of the package being compiled. This CL makes it required when invoking the compiler and adjusts tests that invoke the compiler directly to conform to this new requirement. The go command already passes the flag, so it is unmodified in this CL. It is expected that any other Go build systems also already pass -p, or else they will need to arrange to do so before updating to Go 1.19. Of particular note, Bazel already does for rules with an importpath= attribute, which includes all Gazelle-generated rules. There is more cleanup possible now in cmd/compile, cmd/link, and other consumers of Go object files, but that is left to future CLs. Additional historical background follows but can be ignored. Long ago, before the go command, or modules, or any kind of versioning, symbols in Go archive files were named using just the package name, so that for example func F in math/rand and func F in crypto/rand would both be the object file symbol 'rand.F'. This led to collisions even in small source trees, which made certain packages unusable in the presence of other packages and generally was a problem for Go's goal of scaling to very large source trees. Fixing this problem required changing from package names to import paths in symbol names, which was mostly straightforward. One wrinkle, though, is that the compiler did not know the import path of the package being compiled; it only knew the package name. At the time, there was no go command, just Makefiles that people had invoking 6g (now “go tool compile”) and then copying the resulting object file to an importable location. That is, everyone had a custom build setup for Go, because there was no standard one. So it was not particularly attractive to change how the compiler was invoked, since that would break approximately every Go user at the time. Instead, we arranged for the compiler to emit, and other tools reading object files to recognize, a special import path (the empty string, it turned out) denoting “the import path of this object file”. This worked well enough at the time and maintained complete command-line compatibility with existing Go usage. The changes implementing this transition can be found by searching the Git history for “package global name space”, which is what they eliminated. In particular, CL 190076 (a6736fa4), CL 186263 (758f2bc5), CL 193080 (1cecac81), CL 194053 (19126320), and CL 194071 (531e6b77) did the bulk of this transformation in January 2010. Later, in September 2011, we added the -p flag to the compiler for diagnostic purposes. The problem was that it was easy to create import cycles, especially in tests, and these could not be diagnosed until link time. You'd really want the compiler to diagnose these, for example if the compilation of package sort noticed it was importing a package that itself imported "sort". But the compilation of package sort didn't know its own import path, and so it could not tell whether it had found itself as a transitive dependency. Adding the -p flag solved this problem, and its use was optional, since the linker would still diagnose the import cycle in builds that had not updated to start passing -p. This was CL 4972057 (1e480cd1). There was still no go command at this point, but when we introduced the go command we made it pass -p, which it has for many years at this point. Over time, parts of the compiler began to depend on the presence of the -p flag for various reasonable purposes. For example: In CL 6497074 (041fc8bf; Oct 2012), the race detector used -p to detect packages that should not have race annotations, such as runtime/race and sync/atomic. In CL 13367052 (7276c02b; Sep 2013), a bug fix used -p to detect the compilation of package reflect. In CL 30539 (8aadcc55; Oct 2016), the compiler started using -p to identify package math, to be able to intrinsify calls to Sqrt inside that package. In CL 61019 (9daee931; Sep 2017), CL 71430 (2c1d2e06; Oct 2017), and later related CLs, the compiler started using the -p value when creating various DWARF debugging information. In CL 174657 (cc5eaf93; May 2019), the compiler started writing symbols without the magic empty string whenever -p was used, to reduce the amount of work required in the linker. In CL 179861 (dde7c770; Jun 2019), the compiler made the second argument to //go:linkname optional when -p is used, because in that case the compiler can derive an appropriate default. There are more examples. Today it is impossible to compile the Go standard library without using -p, and DWARF debug information is incomplete without using -p. All known Go build systems pass -p. In particular, the go command does, which is what nearly all Go developers invoke to build Go code. And Bazel does, for go_library rules that set the importpath attribute, which is all rules generated by Gazelle. Gccgo has an equivalent of -p and has required its use in order to disambiguate packages with the same name but different import paths since 2010. On top of all this, various parts of code generation for generics are made more complicated by needing to cope with the case where -p is not specified, even though it's essentially always specified. In summary, the current state is: - Use of the -p flag with cmd/compile is required for building the standard library, and for complete DWARF information, and to enable certain linker speedups. - The go command and Bazel, which we expect account for just about 100% of Go builds, both invoke cmd/compile with -p. - The code in cmd/compile to support builds without -p is complex and has become more complex with generics, but it is almost always dead code and therefore not worth maintaining. - Gccgo already requires its equivalent of -p in any build where two packages have the same name. All this supports the change in this CL, which makes -p required and adjusts tests that invoke cmd/compile to add -p appropriately. Future CLs will be able to remove all the code dealing with the possibility of -p not having been specified. Change-Id: I6b95b9d4cffe59c7bac82eb273ef6c4a67bb0e43 Reviewed-on: https://go-review.googlesource.com/c/go/+/391014 Trust: Russ Cox <rsc@golang.org> Run-TryBot: Russ Cox <rsc@golang.org> TryBot-Result: Gopher Robot <gobot@golang.org> Reviewed-by: Matthew Dempsky <mdempsky@google.com>	2022-03-09 21:31:58 +00:00
Ian Lance Taylor	f1778c28a9	test: recognize and use gc build tag ... Change the run.go driver to recognize the "gc" build tag. Change existing tests to use the "gc" build tag if they use some feature that seems specific to the gc compiler, such as passing specific options to or expecting specific behavior from "go tool compile". Change tests to use the "!gccgo" build tag if they use "go build" or "go run", as while those might work with compilers other than gc, they won't work with the way that gccgo runs its testsuite (which happens independently of the go command). For #43252 Change-Id: I666e04b6d7255a77dfc256ee304094e3a6bb15ad Reviewed-on: https://go-review.googlesource.com/c/go/+/279052 Trust: Ian Lance Taylor <iant@golang.org> Reviewed-by: Cherry Zhang <cherryyz@google.com>	2020-12-18 00:10:44 +00:00
Richard Musiol	e3c684777a	all: skip unsupported tests for js/wasm ... The general policy for the current state of js/wasm is that it only has to support tests that are also supported by nacl. The test nilptr3.go makes assumptions about which nil checks can be removed. Since WebAssembly does not signal on reading a null pointer, all nil checks have to be explicit. Updates #18892 Change-Id: I06a687860b8d22ae26b1c391499c0f5183e4c485 Reviewed-on: https://go-review.googlesource.com/110096 Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org> Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org> TryBot-Result: Gobot Gobot <gobot@golang.org>	2018-04-30 19:39:18 +00:00
Russ Cox	feb6131b1a	cmd/compile: add -linkobj flag to allow writing object file in two parts ... This flag is experimental and the semantics may change even after Go 1.7 is released. There are no changes to code not using the flag. The first part is for reading by future compiles. The second part is for reading by the final link step. Splitting the file this way allows distributed build systems to ship the compile-input part only to compile steps and the linker-input part only to linker steps. The first part is basically just the export data, and the second part is basically everything else. The overall files still have the same broad structure, so that existing tools will work with both halves. It's just that various pieces are empty in the two halves. This also copies the two bits of data the linker needed from export data into the object header proper, so that the linker doesn't need any export data at all. That eliminates a TODO that was left for switching to the binary export data. (Now the linker doesn't need to know about the switch.) The default is still to write out a combined output file. Nothing changes unless you pass -linkobj to the compiler. There is no support in the go command for -linkobj, since the go command doesn't copy objects around. The expectation is that other build systems (like bazel, say) might take advantage of this. The header adjustment and the option for the split output was intended as part of the zip archives, but the zip archives have been cut from Go 1.7. Doing this to the current archives both unblocks one step in the switch to binary export data and enables alternate build systems to experiment with the new flag using the Go 1.7 release. Change-Id: I8b6eab25b8a22b0a266ba0ac6d31e594f3d117f3 Reviewed-on: https://go-review.googlesource.com/22500 Run-TryBot: Russ Cox <rsc@golang.org> TryBot-Result: Gobot Gobot <gobot@golang.org> Reviewed-by: Ian Lance Taylor <iant@golang.org> Reviewed-by: Robert Griesemer <gri@golang.org>	2016-05-09 17:31:45 +00:00