[llvm-symbolizer] Support reading options from environment

llvm-symbolizer is used by sanitizers to symbolize errors discovered by
sanitizer, but there's no way to pass options to llvm-symbolizer since
the tool is invoked directly by the sanitizer runtime. Therefore, we
don't have a way to pass options needed to find debug symbols such as
-dsym-hint or -debug-file-directory. This change enables reading options
from the LLVM_SYMBOLIZER_OPTS in addition to command line which can be
used to pass those additional options to llvm-symbolizer invocations
made by sanitizer runtime.

Differential Revision: https://reviews.llvm.org/D71668

docs/CommandGuide/llvm-addr2line.rst

@@ -27,6 +27,8 @@ Here are some of those differences:
 
 -  Uses `--output-style=GNU`_ by default.
 
+-  Parses options from the environment variable ``LLVM_ADDR2LINE_OPTS``.
+
 SEE ALSO
 --------
 

docs/CommandGuide/llvm-symbolizer.rst

@@ -28,6 +28,12 @@ Object files can be specified together with the addresses either on standard
 input or as positional arguments on the command-line, following any "DATA" or
 "CODE" prefix.
 
+:program:`llvm-symbolizer` parses options from the environment variable
+``LLVM_SYMBOLIZER_OPTS`` after parsing options from the command line.
+``LLVM_SYMBOLIZER_OPTS`` is primarily useful for supplementing the command-line
+options when :program:`llvm-symbolizer` is invoked by another program or
+runtime.
+
 EXAMPLES
 --------
 

test/tools/llvm-symbolizer/options-from-env.test

@@ -0,0 +1,4 @@
+RUN: LLVM_SYMBOLIZER_OPTS=--print-address llvm-symbolizer 0x20112f | FileCheck %s
+RUN: LLVM_ADDR2LINE_OPTS=--print-address llvm-addr2line 0x20112f | FileCheck %s
+
+CHECK: 0x20112f

tools/llvm-symbolizer/llvm-symbolizer.cpp

@@ -289,8 +289,10 @@ int main(int argc, char **argv) {
   }
 
   llvm::sys::InitializeCOMRAII COM(llvm::sys::COMThreadingMode::MultiThreaded);
-  cl::ParseCommandLineOptions(argc, argv, IsAddr2Line ? "llvm-addr2line\n"
-                                                      : "llvm-symbolizer\n");
+  cl::ParseCommandLineOptions(
+      argc, argv, IsAddr2Line ? "llvm-addr2line\n" : "llvm-symbolizer\n",
+      /*Errs=*/nullptr,
+      IsAddr2Line ? "LLVM_ADDR2LINE_OPTS" : "LLVM_SYMBOLIZER_OPTS");
 
   // If both --demangle and --no-demangle are specified then pick the last one.
   if (ClNoDemangle.getPosition() > ClDemangle.getPosition())