[lld] [LLD] [COFF] Pick timestamps from the SOURCE_DATE_EPOCH variable (PR #81326)

[via llvm-commits]

llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-platform-windows

Author: Martin Storsjö (mstorsjo)

<details>
<summary>Changes</summary>

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.

---
Full diff: https://github.com/llvm/llvm-project/pull/81326.diff


2 Files Affected:

- (modified) lld/COFF/Driver.cpp (+9-1) 
- (modified) lld/test/COFF/timestamp.test (+2) 


``````````diff
diff --git a/lld/COFF/Driver.cpp b/lld/COFF/Driver.cpp
index e0afb6b18805b2..22ee2f133be98a 100644
--- a/lld/COFF/Driver.cpp
+++ b/lld/COFF/Driver.cpp
@@ -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
diff --git a/lld/test/COFF/timestamp.test b/lld/test/COFF/timestamp.test
index fbdc5788a33a55..f94eeee8793f01 100644
--- a/lld/test/COFF/timestamp.test
+++ b/lld/test/COFF/timestamp.test
@@ -3,9 +3,11 @@ 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: 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
 
 HASH: ImageFileHeader {
 HASH: TimeDateStamp: [[STAMP:.*]]

``````````

</details>


https://github.com/llvm/llvm-project/pull/81326