Add -gu compiler flag to enforce unwind table generation (including for -betterC)

compiler/src/dmd/backend/backconfig.d

@@ -78,6 +78,7 @@ void out_config_init(
         bool useModuleInfo,
         bool useTypeInfo,
         bool useExceptions,
+        bool unwindTables,
         ubyte dwarf,
         string _version,
         exefmt_t exefmt,
@@ -159,15 +160,16 @@ void out_config_init(
         cfg.avx = avx;
         if (model == 64)
         {
-            cfg.ehmethod = useExceptions ? EHmethod.EH_DWARF : EHmethod.EH_NONE;
+            cfg.ehmethod = (useExceptions || unwindTables) ? EHmethod.EH_DWARF : EHmethod.EH_NONE;
         }
         else
         {
-            cfg.ehmethod = useExceptions ? EHmethod.EH_DWARF : EHmethod.EH_NONE;
+            cfg.ehmethod = (useExceptions || unwindTables) ? EHmethod.EH_DWARF : EHmethod.EH_NONE;
             if (!exe)
                 cfg.flags |= CFGromable; // put switch tables in code segment
         }
-        cfg.flags |= CFGnoebp;
+        if (!unwindTables)
+            cfg.flags |= CFGnoebp;
         switch (pic)
         {
             case 0:         // PIC.fixed
@@ -193,7 +195,7 @@ void out_config_init(
     {
         cfg.fpxmmregs = true;
         cfg.avx = avx;
-        cfg.ehmethod = useExceptions ? EHmethod.EH_DWARF : EHmethod.EH_NONE;
+        cfg.ehmethod = (useExceptions || unwindTables) ? EHmethod.EH_DWARF : EHmethod.EH_NONE;
         cfg.flags |= CFGnoebp;
         if (!exe)
         {
@@ -211,13 +213,13 @@ void out_config_init(
     {
         if (model == 64)
         {
-            cfg.ehmethod = useExceptions ? EHmethod.EH_DWARF : EHmethod.EH_NONE;
+            cfg.ehmethod = (useExceptions || unwindTables) ? EHmethod.EH_DWARF : EHmethod.EH_NONE;
             cfg.fpxmmregs = true;
             cfg.avx = avx;
         }
         else
         {
-            cfg.ehmethod = useExceptions ? EHmethod.EH_DWARF : EHmethod.EH_NONE;
+            cfg.ehmethod = (useExceptions || unwindTables) ? EHmethod.EH_DWARF : EHmethod.EH_NONE;
             if (!exe)
                 cfg.flags |= CFGromable; // put switch tables in code segment
         }
@@ -247,13 +249,13 @@ void out_config_init(
         if (!exe)
             cfg.flags3 |= CFG3pic;
         cfg.objfmt = OBJ_ELF;
-        cfg.ehmethod = useExceptions ? EHmethod.EH_DWARF : EHmethod.EH_NONE;
+        cfg.ehmethod = (useExceptions || unwindTables) ? EHmethod.EH_DWARF : EHmethod.EH_NONE;
     }
     if (cfg.exe == EX_DRAGONFLYBSD64)
     {
         if (model == 64)
         {
-            cfg.ehmethod = useExceptions ? EHmethod.EH_DWARF : EHmethod.EH_NONE;
+            cfg.ehmethod = (useExceptions || unwindTables) ? EHmethod.EH_DWARF : EHmethod.EH_NONE;
             cfg.fpxmmregs = true;
             cfg.avx = avx;
         }
@@ -286,7 +288,7 @@ void out_config_init(
         if (!exe)
             cfg.flags3 |= CFG3pic;
         cfg.objfmt = OBJ_ELF;
-        cfg.ehmethod = useExceptions ? EHmethod.EH_DWARF : EHmethod.EH_NONE;
+        cfg.ehmethod = (useExceptions || unwindTables) ? EHmethod.EH_DWARF : EHmethod.EH_NONE;
     }
 
     cfg.flags2 |= CFG2nodeflib;      // no default library
@@ -357,7 +359,8 @@ static if (0)
 
     cfg.useModuleInfo = useModuleInfo;
     cfg.useTypeInfo = useTypeInfo;
-    cfg.useExceptions = useExceptions;
+    cfg.useExceptions = useExceptions || unwindTables;
+    cfg.unwindTables = unwindTables;
 
     cod3_setdefault();
     if (arm)

compiler/src/dmd/backend/cdef.d

@@ -567,6 +567,7 @@ struct Config
     bool useModuleInfo;         // implement ModuleInfo
     bool useTypeInfo;           // implement TypeInfo
     bool useExceptions;         // implement exception handling
+    bool unwindTables;          // emit unwind tables for stack tracing
     ubyte dwarf;                // DWARF version
 }
 

compiler/src/dmd/backend/dwarfdbginf.d

@@ -109,16 +109,20 @@ static if (1)
      */
     bool doUnwindEhFrame()
     {
-        if (funcsym_p.Sfunc.Fflags3 & Feh_none)
-        {
-            return (config.exe & (EX_FREEBSD | EX_FREEBSD64 | EX_OPENBSD | EX_OPENBSD64 | EX_DRAGONFLYBSD64)) != 0;
-        }
-
         /* FreeBSD fails when having some frames as having unwinding info and some not.
          * (It hangs in unittests for std.datetime.)
          * g++ on FreeBSD does not generate mixed frames, while g++ on OSX and Linux does.
          */
         assert(!(cgstate.usednteh & ~(EHtry | EHcleanup)));
+
+        if (config.unwindTables)
+            return true;
+
+        if (funcsym_p.Sfunc.Fflags3 & Feh_none)
+        {
+            return (config.exe & (EX_FREEBSD | EX_FREEBSD64 | EX_OPENBSD | EX_OPENBSD64 | EX_DRAGONFLYBSD64)) != 0;
+        }
+
         return (cgstate.usednteh & (EHtry | EHcleanup)) ||
                (config.exe & (EX_FREEBSD | EX_FREEBSD64 | EX_OPENBSD | EX_OPENBSD64 | EX_DRAGONFLYBSD64)) && config.useExceptions;
     }
@@ -1759,11 +1763,16 @@ static if (1)
             OutBuffer* buf = SegData[dfseg].SDbuf;
             buf.reserve(1000);
 
-            uint* poffset = ehunwind ? &CIE_offset_unwind : &CIE_offset_no_unwind;
+            // When unwind tables are enabled, don't reference personality function (no druntime)
+            bool usePersonality = ehunwind && !config.unwindTables;
+            uint* poffset = usePersonality ? &CIE_offset_unwind : &CIE_offset_no_unwind;
             if (*poffset == ~0)
-                *poffset = writeEhFrameHeader(dfseg, buf, getRtlsymPersonality(), ehunwind);
+            {
+                Symbol* personality = usePersonality ? getRtlsymPersonality() : null;
+                *poffset = writeEhFrameHeader(dfseg, buf, personality, usePersonality);
+            }
 
-            writeEhFrameFDE(dfseg, sfunc, ehunwind, *poffset);
+            writeEhFrameFDE(dfseg, sfunc, usePersonality, *poffset);
         }
         if (!config.fulltypes)
             return;

compiler/src/dmd/backend/x86/cgcod.d

@@ -642,6 +642,7 @@ void prolog(ref CGstate cg, ref CodeBuilder cdb)
          * so need frame if function can possibly throw
          */
         !(config.exe == EX_WIN32) && !(funcsym_p.Sfunc.Fflags3 & Fnothrow) ||
+        (config.unwindTables && config.ehmethod == EHmethod.EH_DWARF) ||
         cg.accessedTLS ||
         sv64 ||
         (0 && cg.calledafunc && cg.AArch64)

compiler/src/dmd/dmdparams.d

@@ -41,6 +41,7 @@ enum SymImport : ubyte
 struct DMDparams
 {
     bool alwaysframe;       // always emit standard stack frame
+    bool unwindTables;      // emit unwind tables for stack tracing
     ubyte dwarf;            // DWARF version
     bool map;               // generate linker .map file
     bool vasm;              // print generated assembler for each function

compiler/src/dmd/dmsc.d

@@ -88,7 +88,8 @@ void backend_init(const ref Param params, const ref DMDparams driverParams, cons
         driverParams.pic,
         params.useModuleInfo && Module.moduleinfo,
         params.useTypeInfo && Type.dtypeinfo,
-        params.useExceptions && ClassDeclaration.throwable,
+        params.useExceptions && (ClassDeclaration.throwable || driverParams.unwindTables),
+        driverParams.unwindTables,
         driverParams.dwarf,
         global.versionString(),
         exfmt,

compiler/src/dmd/globals.d

@@ -178,6 +178,7 @@ extern (C++) struct Param
     bool useExceptions = true;   // support exception handling
     bool useGC = true;           // support features that require the D runtime GC
     bool betterC;           // be a "better C" compiler; no dependency on D runtime
+    bool unwindTables;      // emit unwind tables for stack tracing (-gu)
     bool addMain;           // add a default main() function
     bool allInst;           // generate code for all template instantiations
     bool bitfields = true;  // support C style bit fields

compiler/src/dmd/globals.h

@@ -202,6 +202,7 @@ struct Param
     d_bool useExceptions; // support exception handling
     d_bool useGC;         // support features that require the D runtime GC
     d_bool betterC;       // be a "better C" compiler; no dependency on D runtime
+    d_bool unwindTables;  // emit unwind tables for stack tracing (-gu)
     d_bool addMain;       // add a default main() function
     d_bool allInst;       // generate code for all template instantiations
     d_bool bitfields;         // support C style bit fields

compiler/src/dmd/glue/toir.d

@@ -106,9 +106,9 @@ struct IRState
         this.params = params;
         this.target = target;
         this.eSink = eSink;
-        mayThrow = params.useExceptions
-            && ClassDeclaration.throwable
-            && !(fd && fd.hasNoEH);
+        bool exceptionsEnabled = params.useExceptions &&
+            (ClassDeclaration.throwable || params.unwindTables);
+        mayThrow = exceptionsEnabled && !(fd && fd.hasNoEH);
         this.Cfile = m.filetype == FileType.c;
     }
 

compiler/src/dmd/mars.d

@@ -985,6 +985,11 @@ bool parseCommandLine(const ref Strings arguments, const size_t argc, out Param
         }
         else if (arg == "-gs")  // https://dlang.org/dmd.html#switch-gs
             driverParams.alwaysframe = true;
+        else if (arg == "-gu")  // https://dlang.org/dmd.html#switch-gu
+        {
+            driverParams.unwindTables = true;
+            global.params.unwindTables = true;
+        }
         else if (arg == "-gx")  // https://dlang.org/dmd.html#switch-gx
             driverParams.stackstomp = true;
         else if (arg == "-lowmem") // https://dlang.org/dmd.html#switch-lowmem