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[LLD] [COFF] Pick timestamps from the SOURCE_DATE_EPOCH variable (llv…
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…m#81326)

The SOURCE_DATE_EPOCH environment variable can be set in order to get
reproducible build.

When linking PE/COFF modules with LLD, the timestamp field is set to the
current time, unless either the /timestamp: or /Brepro option is set. If
neither of them is set, check the SOURCE_DATE_EPOCH variable, before
resorting to using the actual current date and time.

See https://reproducible-builds.org/docs/source-date-epoch/ for reference
on the use of this variable.
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@mstorsjo
mstorsjo authored Feb 10, 2024
1 parent 6a7cf80 commit 0df8aed
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Showing 2 changed files with 27 additions and 1 deletion.
10 changes: 9 additions & 1 deletion lld/COFF/Driver.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -1825,7 +1825,15 @@ void LinkerDriver::linkerMain(ArrayRef<const char *> argsArr) {
}
} else {
config->repro = false;
config->timestamp = time(nullptr);
if (std::optional<std::string> epoch =
Process::GetEnv("SOURCE_DATE_EPOCH")) {
StringRef value(*epoch);
if (value.getAsInteger(0, config->timestamp))
fatal(Twine("invalid SOURCE_DATE_EPOCH timestamp: ") + value +
". Expected 32-bit integer");
} else {
config->timestamp = time(nullptr);
}
}

// Handle /alternatename
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18 changes: 18 additions & 0 deletions lld/test/COFF/timestamp.test
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Original file line number Diff line number Diff line change
Expand Up @@ -3,9 +3,19 @@ RUN: yaml2obj %p/Inputs/generic.yaml -o %t.obj
RUN: lld-link %t.obj /debug /Brepro /entry:main /nodefaultlib /out:%t.1.exe
RUN: lld-link %t.obj /debug /Brepro /entry:main /nodefaultlib /out:%t.2.exe
RUN: lld-link %t.obj /debug /timestamp:0 /entry:main /nodefaultlib /out:%t.3.exe
RUN: env SOURCE_DATE_EPOCH=0 lld-link %t.obj /debug /entry:main /nodefaultlib /out:%t.4.exe
RUN: lld-link %t.obj /debug /timestamp:4294967295 /entry:main /nodefaultlib /out:%t.5.exe
RUN: env SOURCE_DATE_EPOCH=4294967295 lld-link %t.obj /debug /entry:main /nodefaultlib /out:%t.6.exe
RUN: env SOURCE_DATE_EPOCH=12345 lld-link %t.obj /debug /timestamp:0 /entry:main /nodefaultlib /out:%t.7.exe
RUN: env LLD_IN_TEST=1 not lld-link %t.obj /debug /timestamp:4294967296 /entry:main /nodefaultlib /out:%t.8.exe 2>&1 | FileCheck %s --check-prefix=ERROR
RUN: env SOURCE_DATE_EPOCH=4294967296 env LLD_IN_TEST=1 not lld-link %t.obj /debug /entry:main /nodefaultlib /out:%t.9.exe 2>&1 | FileCheck %s --check-prefix=ERROR2
RUN: llvm-readobj --file-headers --coff-debug-directory %t.1.exe | FileCheck %s --check-prefix=HASH
RUN: llvm-readobj --file-headers --coff-debug-directory %t.2.exe | FileCheck %s --check-prefix=HASH
RUN: llvm-readobj --file-headers --coff-debug-directory %t.3.exe | FileCheck %s --check-prefix=ZERO
RUN: llvm-readobj --file-headers --coff-debug-directory %t.4.exe | FileCheck %s --check-prefix=ZERO
RUN: llvm-readobj --file-headers --coff-debug-directory %t.5.exe | FileCheck %s --check-prefix=MAX
RUN: llvm-readobj --file-headers --coff-debug-directory %t.6.exe | FileCheck %s --check-prefix=MAX
RUN: llvm-readobj --file-headers --coff-debug-directory %t.7.exe | FileCheck %s --check-prefix=ZERO

HASH: ImageFileHeader {
HASH: TimeDateStamp: [[STAMP:.*]]
Expand All @@ -16,3 +26,11 @@ ZERO: ImageFileHeader {
ZERO: TimeDateStamp: 1970-01-01 00:00:00 (0x0)
ZERO: DebugDirectory [
ZERO: TimeDateStamp: 1970-01-01 00:00:00 (0x0)

MAX: ImageFileHeader {
MAX: TimeDateStamp: 2106-02-07 06:28:15 (0xFFFFFFFF)
MAX: DebugDirectory [
MAX: TimeDateStamp: 2106-02-07 06:28:15 (0xFFFFFFFF)

ERROR: error: invalid timestamp: 4294967296. Expected 32-bit integer
ERROR2: error: invalid SOURCE_DATE_EPOCH timestamp: 4294967296. Expected 32-bit integer

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