pkid.go

     1  // Copyright 2022 The Go Authors. All rights reserved.
     2  // Use of this source code is governed by a BSD-style
     3  // license that can be found in the LICENSE file.
     4  
     5  package coverage
     6  
     7  // Building the runtime package with coverage instrumentation enabled
     8  // is tricky.  For all other packages, you can be guaranteed that
     9  // the package init function is run before any functions are executed,
    10  // but this invariant is not maintained for packages such as "runtime",
    11  // "internal/cpu", etc. To handle this, hard-code the package ID for
    12  // the set of packages whose functions may be running before the
    13  // init function of the package is complete.
    14  //
    15  // Hardcoding is unfortunate because it means that the tool that does
    16  // coverage instrumentation has to keep a list of runtime packages,
    17  // meaning that if someone makes changes to the pkg "runtime"
    18  // dependencies, unexpected behavior will result for coverage builds.
    19  // The coverage runtime will detect and report the unexpected
    20  // behavior; look for an error of this form:
    21  //
    22  //    internal error in coverage meta-data tracking:
    23  //    list of hard-coded runtime package IDs needs revising.
    24  //    registered list:
    25  //    slot: 0 path='internal/cpu'  hard-coded id: 1
    26  //    slot: 1 path='internal/goarch'  hard-coded id: 2
    27  //    slot: 2 path='internal/runtime/atomic'  hard-coded id: 3
    28  //    slot: 3 path='internal/goos'
    29  //    slot: 4 path='runtime/internal/sys'  hard-coded id: 5
    30  //    slot: 5 path='internal/abi'  hard-coded id: 4
    31  //    slot: 6 path='runtime/internal/math'  hard-coded id: 6
    32  //    slot: 7 path='internal/bytealg'  hard-coded id: 7
    33  //    slot: 8 path='internal/goexperiment'
    34  //    slot: 9 path='internal/runtime/syscall'  hard-coded id: 8
    35  //    slot: 10 path='runtime'  hard-coded id: 9
    36  //    fatal error: runtime.addCovMeta
    37  //
    38  // For the error above, the hard-coded list is missing "internal/goos"
    39  // and "internal/goexperiment" ; the developer in question will need
    40  // to copy the list above into "rtPkgs" below.
    41  //
    42  // Note: this strategy assumes that the list of dependencies of
    43  // package runtime is fixed, and doesn't vary depending on OS/arch. If
    44  // this were to be the case, we would need a table of some sort below
    45  // as opposed to a fixed list.
    46  
    47  var rtPkgs = [...]string{
    48  	"internal/cpu",
    49  	"internal/goarch",
    50  	"internal/runtime/atomic",
    51  	"internal/goos",
    52  	"internal/chacha8rand",
    53  	"runtime/internal/sys",
    54  	"internal/abi",
    55  	"runtime/internal/math",
    56  	"internal/bytealg",
    57  	"internal/goexperiment",
    58  	"internal/runtime/syscall",
    59  	"runtime",
    60  }
    61  
    62  // Scoping note: the constants and apis in this file are internal
    63  // only, not expected to ever be exposed outside of the runtime (unlike
    64  // other coverage file formats and APIs, which will likely be shared
    65  // at some point).
    66  
    67  // NotHardCoded is a package pseudo-ID indicating that a given package
    68  // is not part of the runtime and doesn't require a hard-coded ID.
    69  const NotHardCoded = -1
    70  
    71  // HardCodedPkgID returns the hard-coded ID for the specified package
    72  // path, or -1 if we don't use a hard-coded ID. Hard-coded IDs start
    73  // at -2 and decrease as we go down the list.
    74  func HardCodedPkgID(pkgpath string) int {
    75  	for k, p := range rtPkgs {
    76  		if p == pkgpath {
    77  			return (0 - k) - 2
    78  		}
    79  	}
    80  	return NotHardCoded
    81  }
    82
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