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diff --git a/www/text.causal.agency/003-pleasant-c.7 b/www/text.causal.agency/003-pleasant-c.7 new file mode 100644 index 00000000..16030b7e --- /dev/null +++ b/www/text.causal.agency/003-pleasant-c.7 @@ -0,0 +1,120 @@ +.Dd September 30, 2018 +.Dt PLEASANT-C 7 +.Os "Causal Agency" +. +.Sh NAME +.Nm Pleasant C +.Nd it's good, actually +. +.Sh DESCRIPTION +I've been writing a lot of C lately +and actually find it very pleasant. +I want to talk about some of its ergonomic features. +These are C99 features unless otherwise noted. +. +.Ss Initializer syntax +Struct and union initializer syntax +is well generalized. +Designators can be chained, +making initializing nested structs easy, +and all uninitialized fields are zeroed. +. +.Bd -literal -offset indent +struct { + struct pollfd fds[2]; +} loop = { + .fds[0].fd = STDIN_FILENO, + .fds[1].fd = STDOUT_FILENO, + .fds[0].events = POLLIN, + .fds[1].events = POLLOUT, +}; +.Ed +. +.Ss Variable-length arrays +VLAs can be multi-dimensional, +which can avoid manual stride multiplications +needed to index a flat +.Xr malloc 3 Ap d +array. +. +.Bd -literal -offset indent +uint8_t glyphs[len][height][width]; +fread(glyphs, height * width, len, stdin); +.Ed +. +.Ss Incomplete array types +The last field of a struct can be an +.Dq incomplete +array type, +which means it doesn't have a length. +A variable amount of space for the struct can be +.Xr malloc 3 Ap d , +or the struct can be used as +a sort of pointer with fields. +. +.Bd -literal -offset indent +struct Line { + enum Filter type; + uint8_t data[]; +} *line = &png.data[1 + lineSize()]; +.Ed +. +.Ss Anonymous struct and union fields (C11) +Members of structs or unions +which are themselves structs or unions +can be unnamed. +In that case, +each of the inner fields +is treated as a member of the outer struct or union. +This makes working with tagged unions nicer. +. +.Bd -literal -offset indent +struct Message { + enum { Foo, Bar } type; + union { + uint8_t foo; + uint32_t bar; + }; +} msg = { .type = Foo, .foo = 0xFF }; +.Ed +. +.Ss Static assert (C11) +Assertions can be made at compile time. +Most useful for checking sizes of structs. +. +.Bd -literal -offset indent +static_assert(13 == sizeof(struct PNGHeader), "PNG IHDR size"); +.Ed +. +.Ss Leading-break switch +This one is just an odd style choice +I came across that C happens to allow. +To prevent accidental fall-through +in switch statements, +you can put breaks before the case labels. +. +.Bd -literal -offset indent +while (0 < (opt = getopt(argc, argv, "h:w:"))) { + switch (opt) { + break; case 'h': height = optarg; + break; case 'w': width = optarg; + break; default: return EX_USAGE; + } +} +.Ed +. +.Sh AUTHORS +.An Mt june@causal.agency +. +.Pp +This document is produced from +.Xr mdoc 7 +source available from +.Lk https://git.causal.agency/src/tree/www/text.causal.agency +. +.Sh CAVEATS +This isn't meant to be advice. +It's just how I like to write C, +and I don't +.Dq ship +software in C. |