Merging r352806:
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r352806 | sbc | 2019-01-31 14:38:22 -0800 (Thu, 31 Jan 2019) | 5 lines
[WebAssembly] MC: Fix for outputing wasm object to /dev/null
Subscribers: dschuff, jgravelle-google, aheejin, sunfish, llvm-commits
Differential Revision: https://reviews.llvm.org/D57479
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llvm-svn: 360949
diff --git a/llvm/lib/MC/WasmObjectWriter.cpp b/llvm/lib/MC/WasmObjectWriter.cpp
index 333748d..b07fe05 100644
--- a/llvm/lib/MC/WasmObjectWriter.cpp
+++ b/llvm/lib/MC/WasmObjectWriter.cpp
@@ -368,7 +368,13 @@
// Now that the section is complete and we know how big it is, patch up the
// section size field at the start of the section.
void WasmObjectWriter::endSection(SectionBookkeeping &Section) {
- uint64_t Size = W.OS.tell() - Section.PayloadOffset;
+ uint64_t Size = W.OS.tell();
+ // /dev/null doesn't support seek/tell and can report offset of 0.
+ // Simply skip this patching in that case.
+ if (!Size)
+ return;
+
+ Size -= Section.PayloadOffset;
if (uint32_t(Size) != Size)
report_fatal_error("section size does not fit in a uint32_t");
diff --git a/llvm/test/MC/WebAssembly/null-output.s b/llvm/test/MC/WebAssembly/null-output.s
new file mode 100644
index 0000000..a25d095
--- /dev/null
+++ b/llvm/test/MC/WebAssembly/null-output.s
@@ -0,0 +1,10 @@
+# RUN: llvm-mc -triple=wasm32-unknown-unknown -filetype=obj -o /dev/null < %s
+
+ .text
+ .section .text.main,"",@
+ .type main,@function
+main:
+ .functype main (i32, i32) -> (i32)
+ end_function
+.Lfunc_end0:
+ .size main, .Lfunc_end0-main
