Bug 7056 – weird segfault in std.conv.to

import std.conv; import std.math; void main() { import std.stdio; vec3 w = vec3(); writefln("%f w: %f", 3.5f, w.length); } struct Vector(T, int dim) { union { struct { T x = 0; T y = 0; T z = 0; } T[dim] cell; } string toString() { return to!string(cell); } /// return length*length @property T sqLength() { return cast()x * x + y * y + z * z; } /// return the vector length @property T length() { toString; auto ret = sqLength; return sqrt(ret); } } alias Vector!(float, 3) vec3; $ dmd -debug -gc vector.d && gdb --batch -ex 'run' -ex 'bt 15' ./vector Program received signal SIGSEGV, Segmentation fault. 0x00007ffff7669faa in snprintf () from /lib/x86_64-linux-gnu/libc.so.6 #0 0x00007ffff7669faa in snprintf () from /lib/x86_64-linux-gnu/libc.so.6 #1 0x000000000044affe in void std.format.formatValue!(std.array.Appender!(immutable(char)[]).Appender, float, char).formatValue(std.array.Appender!(immutable(char)[]).Appender, float, ref std.format.FormatSpec!(char).FormatSpec) (f=0x7fffffffdcd8, obj=0, w=...) at /home/trass3r/coding/dmd/linux/bin64/../../src/phobos/std/format.d:1204 #2 0x000000000044b387 in void std.format.formatElement!(std.array.Appender!(immutable(char)[]).Appender, float, char).formatElement(std.array.Appender!(immutable(char)[]).Appender, float, ref std.format.FormatSpec!(char).FormatSpec) (f=0x7fffffffdcd8, val=0, w=...) at /home/trass3r/coding/dmd/linux/bin64/../../src/phobos/std/format.d:1596 #3 0x000000000044a661 in void std.format.formatRange!(std.array.Appender!(immutable(char)[]).Appender, float[], char).formatRange(std.array.Appender!(immutable(char)[]).Appender, float[], ref std.format.FormatSpec!(char).FormatSpec) (f=0x7fffffffdcd8, val=0x00007fffffffdd780000000000000003, w=...) at /home/trass3r/coding/dmd/linux/bin64/../../src/phobos/std/format.d:1452 #4 0x000000000044a50f in void std.format.formatValue!(std.array.Appender!(immutable(char)[]).Appender, float[], char).formatValue(std.array.Appender!(immutable(char)[]).Appender, float[], ref std.format.FormatSpec!(char).FormatSpec) (f=0x7fffffffdcd8, val=0x00007fffffffdd780000000000000003, w=...) at /home/trass3r/coding/dmd/linux/bin64/../../src/phobos/std/format.d:1386 #5 0x000000000044a4dd in immutable(char)[] std.conv.toStr!(immutable(char)[], float[]).toStr(float[]) (src=0x00007fffffffdd780000000000000003) at /home/trass3r/coding/dmd/linux/bin64/../../src/phobos/std/conv.d:94 #6 0x000000000044a48f in immutable(char)[] std.conv.toImpl!(immutable(char)[], float[]).toImpl(float[]) (s=0x00007fffffffdd780000000000000003) at /home/trass3r/coding/dmd/linux/bin64/../../src/phobos/std/conv.d:803 #7 0x000000000044a401 in immutable(char)[] std.conv.toImpl!(immutable(char)[], float[3]).toImpl(ref float[3]) (s=0x7fffffffdd78) at /home/trass3r/coding/dmd/linux/bin64/../../src/phobos/std/conv.d:353 #8 0x000000000044a381 in immutable(char)[] std.conv.to!(immutable(char)[]).to!(float[3]).to(float[3]) (_param_0=...) at /home/trass3r/coding/dmd/linux/bin64/../../src/phobos/std/conv.d:237 #9 0x0000000000442d3f in immutable(char)[] vector.Vector!(float, 3).Vector.toString() (this=0x7fffffffde10) at vector.d:25 #10 0x0000000000442df6 in @property float vector.Vector!(float, 3).Vector.length() (this=0x7fffffffde10) at vector.d:36

I can't reproduce this bug in git HEAD (1a6da16ef112e03607574758b722698f2950b0de) running on Linux/64. Could you check to see if it still occurs either in the latest release or in git HEAD? Since it's been a while, the bug may have been fixed already.

It's probably a good idea to add this code to a unittest in std.conv, to prevent regressions in the future.